##### 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]
```

self._tqm.clear_failed_hosts()
                    iterator._host_states[host.name] = prev_host_state
                    for method, what in status_to_stats_map:
                        if getattr(result, method)():
                            self._tqm._stats.decrement(what, host.name)
                    self._tqm._stats.decrement('ok', host.name)
                    
                    self._queue_task(host, task, task_vars, play_context)
                    _processed_results.extend(debug_closure(func)(self, iterator, one_pass))
                    break
                elif next_action.result == NextAction.CONTINUE:
                    _processed_results.append(result)
                    break
                elif next_action.result == NextAction.EXIT:
                    
                    sys.exit(99)
            else:
                _processed_results.append(result)
        return _processed_results
    return inner
class StrategyBase:
    '''
    This is the base class for strategy plugins, which contains some common
    code useful to all strategies like running handlers, cleanup actions, etc.
    '''
    
    
    
    ALLOW_BASE_THROTTLING = True
    def __init__(self, tqm):