##### SUMMARY
Setting `extended: yes` in `loop_control` doesn't provide `ansible_loop` inside the loop.

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
loop_control

##### ANSIBLE VERSION
```
ansible 2.9.0.dev0
  config file = None
  configured module search path = ['/home/kustodian/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /home/kustodian/git/github/ansible/lib/ansible
  executable location = /home/kustodian/git/github/ansible/bin/ansible
  python version = 3.7.4 (default, Jul 16 2019, 07:12:58) [GCC 9.1.0]
```
This also doesn't work on 2.8.4

##### CONFIGURATION
```
```

##### OS / ENVIRONMENT
ArchLinux

##### STEPS TO REPRODUCE
Create two files:
```yaml
# play.yml
---
- hosts: localhost
  connection: local
  tasks:
    - include_tasks: inner.yml
      loop:
        - 1
        - 2
        - 3
      loop_control:
        extended: yes
```
```
# inner.yml
- debug:
    var: ansible_loop
```
and run:
```
ansible-playbook play.yml -i localhost,
```

##### EXPECTED RESULTS
Ansible should print the value of `ansible_loop` three times.

##### ACTUAL RESULTS
It actually prints that `ansible_loop` is undefined:
```
$ ansible-playbook play.yml -i localhost,

PLAY [localhost] *******************************************************************************************************************************************************************************************

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

TASK [include_tasks] ***************************************************************************************************************************************************************************************
included: /tmp/inner.yml for localhost
included: /tmp/inner.yml for localhost
included: /tmp/inner.yml for localhost

TASK [debug] ***********************************************************************************************************************************************************************************************
ok: [localhost] => {
    "ansible_loop": "VARIABLE IS NOT DEFINED!"
}

TASK [debug] ***********************************************************************************************************************************************************************************************
ok: [localhost] => {
    "ansible_loop": "VARIABLE IS NOT DEFINED!"
}

TASK [debug] ***********************************************************************************************************************************************************************************************
ok: [localhost] => {
    "ansible_loop": "VARIABLE IS NOT DEFINED!"
}

PLAY RECAP *************************************************************************************************************************************************************************************************
localhost                  : ok=7    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0
```

cumulative_path = parent_include_dir
                                    include_target = templar.template(include_result['include'])
                                    if original_task._role:
                                        new_basedir = os.path.join(original_task._role._role_path, 'tasks', cumulative_path)
                                        candidates = [loader.path_dwim_relative(original_task._role._role_path, 'tasks', include_target),
                                                      loader.path_dwim_relative(new_basedir, 'tasks', include_target)]
                                        for include_file in candidates:
                                            try:
                                                
                                                os.stat(include_file)
                                                
                                                break
                                            except OSError:
                                                pass
                                    else:
                                        include_file = loader.path_dwim_relative(loader.get_basedir(), cumulative_path, include_target)
                                    if os.path.exists(include_file):
                                        break
                                    else:
                                        parent_include = parent_include._parent
                        if include_file is None:
                            if original_task._role:
                                include_target = templar.template(include_result['include'])
                                include_file = loader.path_dwim_relative(original_task._role._role_path, 'tasks', include_target)
                            else:
                                include_file = loader.path_dwim(include_result['include'])
                        include_file = templar.template(include_file)
                        inc_file = IncludedFile(include_file, include_args, special_vars, original_task)
                    else: