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##### SUMMARY
The `reboot` module does not work with `async`, `poll`, and `async_status`. Suppose I have 10 nodes to reboot, but I can only set `fork` to 2. The `reboot` module will reboot 2 nodes at a time. I tried using `async`, `poll`, and `async_status` to kick of the reboots on the 10 nodes, 2 at a time, and then poll for the results. `async` and `poll` seem to do nothing on the `reboot` module as the behavior remains the same as without them.

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
`reboot` module

##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
```paste below
ansible 2.9.12
  config file = /etc/ansible/ansible.cfg
  configured module search path = ['/home/user/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/lib64/python3.6/site-packages/ansible
  executable location = /usr/bin/ansible
  python version = 3.6.8 (default, May  2 2019, 19:37:42) [GCC 4.4.7 20120313 (Red Hat 4.4.7-23)]
```

##### CONFIGURATION
<!--- Paste verbatim output from "ansible-config dump --only-changed" between quotes -->
```paste below
ANSIBLE_PIPELINING(/etc/ansible/ansible.cfg) = True
ANSIBLE_SSH_ARGS(/etc/ansible/ansible.cfg) = -o ControlMaster=auto -o ControlPersist=60s -o UserKnownHostsFile=/dev/null
ANSIBLE_SSH_RETRIES(/etc/ansible/ansible.cfg) = 2
COMMAND_WARNINGS(/etc/ansible/ansible.cfg) = False
DEFAULT_FORKS(/etc/ansible/ansible.cfg) = 2
DEFAULT_GATHERING(/etc/ansible/ansible.cfg) = explicit
DEFAULT_TIMEOUT(/etc/ansible/ansible.cfg) = 40
HOST_KEY_CHECKING(/etc/ansible/ansible.cfg) = False
RETRY_FILES_ENABLED(/etc/ansible/ansible.cfg) = False
```

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


##### STEPS TO REPRODUCE
<!--- Describe exactly how to reproduce the problem, using a minimal test-case -->
Described in the summary

<!--- Paste example playbooks or commands between quotes below -->
```yaml

```

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

##### EXPECTED RESULTS
<!--- Describe what you expected to happen when running the steps above -->
I expect the `reboot` module to start the reboot on 2 nodes, then move on to something else (like start the reboot on another 2 nodes), then come back to check on the results of the reboots by using `async`, `poll`, and `async_status`.

##### ACTUAL RESULTS
<!--- Describe what actually happened. If possible run with extra verbosity (-vvvv) -->
The `reboot` module ignores `async` and `poll`.

<!--- Paste verbatim command output between quotes -->
```paste below

```

if shutdown_bin[0] == '/':
            return shutdown_bin
        else:
            default_search_paths = ['/sbin', '/bin', '/usr/sbin', '/usr/bin', '/usr/local/sbin']
            search_paths = self._task.args.get('search_paths', default_search_paths)
            try:
                
                search_paths = check_type_list(search_paths)
            except TypeError:
                err_msg = "'search_paths' must be a string or flat list of strings, got {0}"
                raise AnsibleError(err_msg.format(search_paths))
            display.debug('{action}: running find module looking in {paths} to get path for "{command}"'.format(
                action=self._task.action,
                command=shutdown_bin,
                paths=search_paths))
            find_result = self._execute_module(
                task_vars=task_vars,
                
                module_name='ansible.legacy.find',
                module_args={
                    'paths': search_paths,
                    'patterns': [shutdown_bin],
                    'file_type': 'any'
                }
            )
            full_path = [x['path'] for x in find_result['files']]
            if not full_path:
                raise AnsibleError('Unable to find command "{0}" in search paths: {1}'.format(shutdown_bin, search_paths))
            return full_path[0]
    def deprecated_args(self):