##### 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
```

include_results = res._result['results']
                else:
                    include_results = [res._result]
                for include_result in include_results:
                    
                    if 'skipped' in include_result and include_result['skipped'] or 'failed' in include_result and include_result['failed']:
                        continue
                    cache_key = (iterator._play, original_host, original_task)
                    try:
                        task_vars = task_vars_cache[cache_key]
                    except KeyError:
                        task_vars = task_vars_cache[cache_key] = variable_manager.get_vars(play=iterator._play, host=original_host, task=original_task)
                    include_args = include_result.get('include_args', dict())
                    special_vars = {}
                    loop_var = include_result.get('ansible_loop_var', 'item')
                    index_var = include_result.get('ansible_index_var')
                    if loop_var in include_result:
                        task_vars[loop_var] = special_vars[loop_var] = include_result[loop_var]
                    if index_var and index_var in include_result:
                        task_vars[index_var] = special_vars[index_var] = include_result[index_var]
                    if '_ansible_item_label' in include_result:
                        task_vars['_ansible_item_label'] = special_vars['_ansible_item_label'] = include_result['_ansible_item_label']
                    if original_task.no_log and '_ansible_no_log' not in include_args:
                        task_vars['_ansible_no_log'] = special_vars['_ansible_no_log'] = original_task.no_log
                    
                    
                    task_vars['ansible_search_path'] = original_task.get_search_path()
                    
                    if loader.get_basedir() not in task_vars['ansible_search_path']:
                        task_vars['ansible_search_path'].append(loader.get_basedir())