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##### SUMMARY
<!--- Explain the problem briefly below -->
When providing `ansible-pull` with multiple playbooks (e.g. `ansible-pull [...] playbook1.yml playbook2.yml`), only the first playbook is run.

This is contrary to what the documentation states is possible:
* https://docs.ansible.com/ansible/2.10/cli/ansible-pull.html - the usage block in the synopsis section shows multiple playbooks (`[playbook.yml [playbook.yml ...]]`), just like `ansible-playbook`.

The `argparse` options indicate support for multiple playbooks, and call the arguments `Playbook(s)` - https://github.com/ansible/ansible/blob/v2.9.13/lib/ansible/cli/pull.py#L86

However, the code only ever seems to handle a single playbook - https://github.com/ansible/ansible/blob/v2.9.13/lib/ansible/cli/pull.py#L314-L320

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
<!--- Write the short name of the module, plugin, task or feature below, use your best guess if unsure -->
ansible-pull

##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
```paste below
ansible 2.9.13
  config file = /root/.ansible/pull/ip-x-x-x-x.ec2.internal/ansible.cfg
  configured module search path = [u'/root/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/lib/python2.7/site-packages/ansible
  executable location = /usr/bin/ansible
  python version = 2.7.18 (default, Aug 27 2020, 21:23:25) [GCC 7.3.1 20180712 (Red Hat 7.3.1-9)]
```

##### CONFIGURATION
<!--- Paste verbatim output from "ansible-config dump --only-changed" between quotes -->
```paste below
DEFAULT_FORCE_HANDLERS(/root/.ansible/pull/ip-x-x-x-x.ec2.internal/ansible.cfg) = True
DEFAULT_FORKS(/root/.ansible/pull/ip-x-x-x-x.ec2.internal/ansible.cfg) = 25
DEFAULT_HOST_LIST(/root/.ansible/pull/ip-x-x-x-x.ec2.internal/ansible.cfg) = [u'/root/.ansible/pull/ip-x-x-x-x.ec2.internal/hosts.ini']
DEFAULT_LOG_PATH(/root/.ansible/pull/ip-x-x-x-x.ec2.internal/ansible.cfg) = /root/.ansible/pull/ip-x-x-x-x.ec2.internal/ansible.log
DEFAULT_POLL_INTERVAL(/root/.ansible/pull/ip-x-x-x-x.ec2.internal/ansible.cfg) = 5
DEFAULT_STRATEGY(/root/.ansible/pull/ip-x-x-x-x.ec2.internal/ansible.cfg) = linear
```

##### OS / ENVIRONMENT
<!--- Provide all relevant information below, e.g. target OS versions, network device firmware, etc. -->
Amazon Linux 2

##### STEPS TO REPRODUCE
<!--- Describe exactly how to reproduce the problem, using a minimal test-case -->
Run `ansible-pull` with multiple playbooks, for example:

```bash
ansible-pull --url git@github.com:NFarrington/demo-ansible-pull-multiple-playbooks.git --inventory 127.0.0.1, playbook1.yml playbook2.yml
```

<!--- Paste example playbooks or commands between quotes below -->
Playbook 1:
```yaml
---
- name: Playbook1
  hosts: all
  tasks:
  - name: playbook1 debug message
    debug:
      msg: Hello from playbook1
```

Playbook 2:
```yaml
---
- name: Playbook2
  hosts: all
  tasks:
  - name: playbook2 debug message
    debug:
      msg: Hello from playbook2
```

<!--- HINT: You can paste gist.github.com links for larger files -->

##### EXPECTED RESULTS
<!--- Describe what you expected to happen when running the steps above -->

The same behaviour as `ansible-playbook` is expected:

```
PLAY [Playbook1] *************************************************************************************

TASK [Gathering Facts] *******************************************************************************
ok: [127.0.0.1]

TASK [playbook1 debug message] ***********************************************************************
ok: [127.0.0.1] => {
    "msg": "Hello from playbook1"
}

PLAY RECAP *******************************************************************************************
127.0.0.1                  : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   


PLAY [Playbook2] *************************************************************************************

TASK [Gathering Facts] *******************************************************************************
ok: [127.0.0.1]

TASK [playbook2 debug message] ***********************************************************************
ok: [127.0.0.1] => {
    "msg": "Hello from playbook2"
}

PLAY RECAP *******************************************************************************************
127.0.0.1                  : ok=4    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   
```

##### ACTUAL RESULTS
<!--- Describe what actually happened. If possible run with extra verbosity (-vvvv) -->

Only the first playbook is executed:

<!--- Paste verbatim command output between quotes -->
```paste below
PLAY [Playbook1] *************************************************************************************

TASK [Gathering Facts] *******************************************************************************
ok: [127.0.0.1]

TASK [playbook1 debug message] ***********************************************************************
ok: [127.0.0.1] => {
    "msg": "Hello from playbook1"
}

PLAY RECAP *******************************************************************************************
127.0.0.1                  : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   
```

inv_opts = self._get_inv_cli()
        if not inv_opts:
            inv_opts = " -i localhost, "
            
            inv_opts += '-e %s ' % shlex_quote('ansible_python_interpreter=%s' % sys.executable)
        
        if context.CLIARGS['module_name'] == 'git':
            repo_opts = "name=%s dest=%s" % (context.CLIARGS['url'], context.CLIARGS['dest'])
            if context.CLIARGS['checkout']:
                repo_opts += ' version=%s' % context.CLIARGS['checkout']
            if context.CLIARGS['accept_host_key']:
                repo_opts += ' accept_hostkey=yes'
            if context.CLIARGS['private_key_file']:
                repo_opts += ' key_file=%s' % context.CLIARGS['private_key_file']
            if context.CLIARGS['verify']:
                repo_opts += ' verify_commit=yes'
            if context.CLIARGS['tracksubs']:
                repo_opts += ' track_submodules=yes'
            if not context.CLIARGS['fullclone']:
                repo_opts += ' depth=1'
        elif context.CLIARGS['module_name'] == 'subversion':
            repo_opts = "repo=%s dest=%s" % (context.CLIARGS['url'], context.CLIARGS['dest'])
            if context.CLIARGS['checkout']:
                repo_opts += ' revision=%s' % context.CLIARGS['checkout']
            if not context.CLIARGS['fullclone']:
                repo_opts += ' export=yes'
        elif context.CLIARGS['module_name'] == 'hg':
            repo_opts = "repo=%s dest=%s" % (context.CLIARGS['url'], context.CLIARGS['dest'])
            if context.CLIARGS['checkout']: