<!--- Verify first that your issue is not already reported on GitHub -->
<!--- Also test if the latest release and devel branch are affected too -->
<!--- Complete *all* sections as described, this form is processed automatically -->

##### SUMMARY
<!--- Explain the problem briefly below -->
When looping `include_tasks`, the loop control `loop_var` property is not defined in the included task, when the `loop_var` property has been assigned with a template.

##### ISSUE TYPE
- Bug Report

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

##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
```paste below
ansible 2.8.1
  config file = /playbooks/ansible.cfg
  configured module search path = ['/root/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/local/lib/python3.7/site-packages/ansible
  executable location = /usr/local/bin/ansible
  python version = 3.7.3 (default, Jun 11 2019, 01:05:09) [GCC 6.3.0 20170516]
```

##### OS / ENVIRONMENT
<!--- Provide all relevant information below, e.g. target OS versions, network device firmware, etc. -->
Redhat7
Archlinux


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

<!--- Paste example playbooks or commands between quotes below -->
```yaml
---
# main.yml
- hosts: localhost
  vars:
    loop_var_name: custom_var

  tasks:
    - include_tasks: looped-include.yml
      loop:
        - first
        - second
      loop_control:
        loop_var: "{{ loop_var_name }}"
```

```yaml
---
# looped-include.yml
- name: Print looped var
  debug:
    var: custom_var

- name: Loop default item var
  debug:
    var: item
```

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

##### EXPECTED RESULTS
<!--- Describe what you expected to happen when running the steps above -->
We expect the variabe `custom_var` to be the looped variable, and `item` to be undefined. 

##### ACTUAL RESULTS
<!--- Describe what actually happened. If possible run with extra verbosity (-vvvv) -->
Neither `custom_var` nor `item` are defined in the looped included task.

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

TASK [Gathering Facts] ***********************************************************************************
ok: [localhost]
included: /ansible-bug/looped-include.yml for localhost
included: /ansible-bug/looped-include.yml for localhost

TASK [Print looped var] **********************************************************************************
ok: [localhost] => 
  custom_var: VARIABLE IS NOT DEFINED!

TASK [Loop default item var] *****************************************************************************
ok: [localhost] => 
  item: VARIABLE IS NOT DEFINED!

TASK [Print looped var] **********************************************************************************
ok: [localhost] => 
  custom_var: VARIABLE IS NOT DEFINED!

TASK [Loop default item var] *****************************************************************************
ok: [localhost] => 
  item: VARIABLE IS NOT DEFINED!
```

display.warning(u"The loop variable '%s' is already in use. "
                            u"You should set the `loop_var` value in the `loop_control` option for the task"
                            u" to something else to avoid variable collisions and unexpected behavior." % loop_var)
        ran_once = False
        if self._task.loop_with:
            
            items = self._squash_items(items, loop_var, task_vars)
        no_log = False
        items_len = len(items)
        for item_index, item in enumerate(items):
            task_vars['ansible_loop_var'] = loop_var
            task_vars[loop_var] = item
            if index_var:
                task_vars[index_var] = item_index
            if extended:
                task_vars['ansible_loop'] = {
                    'allitems': items,
                    'index': item_index + 1,
                    'index0': item_index,
                    'first': item_index == 0,
                    'last': item_index + 1 == items_len,
                    'length': items_len,
                    'revindex': items_len - item_index,
                    'revindex0': items_len - item_index - 1,
                }
                try:
                    task_vars['ansible_loop']['nextitem'] = items[item_index + 1]
                except IndexError:
                    pass
                if item_index - 1 >= 0: