##### 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]
```

templar = Templar(loader=self._loader, variables=all_vars)
            
            
            
            play_context = play_context.set_task_and_variable_override(task=task, variables=all_vars, templar=templar)
            
            
            play_context.post_validate(templar=templar)
            
            
            if not play_context.remote_addr:
                play_context.remote_addr = target_host.address
            
            
            play_context.update_vars(all_vars)
            if task.when:
                self._cond_not_supported_warn(meta_action)
            if target_host in self._active_connections:
                connection = Connection(self._active_connections[target_host])
                del self._active_connections[target_host]
            else:
                connection = plugin_loader.connection_loader.get(play_context.connection, play_context, os.devnull)
                play_context.set_attributes_from_plugin(connection)
            if connection:
                try:
                    connection.reset()
                    msg = 'reset connection'
                except ConnectionError as e:
                    
                    display.debug("got an error while closing persistent connection: %s" % e)