##### 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]
```

'''
        Wait for the handler tasks to complete, using a short sleep
        between checks to ensure we don't spin lock
        '''
        ret_results = []
        handler_results = 0
        display.debug("waiting for handler results...")
        while (self._pending_handler_results > 0 and
               handler_results < len(notified_hosts) and
               not self._tqm._terminated):
            if self._tqm.has_dead_workers():
                raise AnsibleError("A worker was found in a dead state")
            results = self._process_pending_results(iterator, do_handlers=True)
            ret_results.extend(results)
            handler_results += len([
                r._host for r in results if r._host in notified_hosts and
                r.task_name == handler.name])
            if self._pending_handler_results > 0:
                time.sleep(C.DEFAULT_INTERNAL_POLL_INTERVAL)
        display.debug("no more pending handlers, returning what we have")
        return ret_results
    def _wait_on_pending_results(self, iterator):