##### SUMMARY
add_host will return 'changed' for every invocation, it does not matter if the host already existed and no changes were actually made to inventory

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
<!--- Write the short name of the module, plugin, task or feature below, use your best guess if unsure -->
add_host
##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
```paste below
2.7, 2.8, 2.9, 2.10
```

##### CONFIGURATION
<!--- Paste verbatim output from "ansible-config dump --only-changed" between quotes -->
```paste below

```

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

##### STEPS TO REPRODUCE

Simplest example, but also happens when specifying variables and/or groups

test.yml
```yaml
- hosts: localhost
  gather_facts: false
  tasks:
    - add_host: name=testhost
```
test_inv.ini
```ini
testhost
```
run:
``` ansible-playbook -i test_inv.ini test.yml```

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

##### EXPECTED RESULTS
<!--- Describe what you expected to happen when running the steps above -->
```
 _________________
< TASK [add_host] >
 -----------------
       \   ,__,
        \  (oo)____
           (__)    )\
              ||--|| *

OK: [localhost]
```

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

<!--- Paste verbatim command output between quotes -->
```paste below
 _________________
< TASK [add_host] >
 -----------------
       \   ,__,
        \  (oo)____
           (__)    )\
              ||--|| *

changed: [localhost]
```

else:
                    self._tqm._stats.increment('ok', original_host.name)
                    self._tqm._stats.increment('ignored', original_host.name)
                    if 'changed' in task_result._result and task_result._result['changed']:
                        self._tqm._stats.increment('changed', original_host.name)
                self._tqm.send_callback('v2_runner_on_failed', task_result, ignore_errors=ignore_errors)
            elif task_result.is_unreachable():
                ignore_unreachable = original_task.ignore_unreachable
                if not ignore_unreachable:
                    self._tqm._unreachable_hosts[original_host.name] = True
                    iterator._play._removed_hosts.append(original_host.name)
                else:
                    self._tqm._stats.increment('skipped', original_host.name)
                    task_result._result['skip_reason'] = 'Host %s is unreachable' % original_host.name
                self._tqm._stats.increment('dark', original_host.name)
                self._tqm.send_callback('v2_runner_on_unreachable', task_result)
            elif task_result.is_skipped():
                self._tqm._stats.increment('skipped', original_host.name)
                self._tqm.send_callback('v2_runner_on_skipped', task_result)
            else:
                role_ran = True
                if original_task.loop:
                    
                    
                    result_items = task_result._result.get('results', [])
                else:
                    result_items = [task_result._result]
                for result_item in result_items:
                    if '_ansible_notify' in result_item:
                        if task_result.is_changed():