##### 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]
```

'''
        Reads results off the final queue and takes appropriate action
        based on the result (executing callbacks, updating state, etc.).
        '''
        ret_results = []
        handler_templar = Templar(self._loader)
        def get_original_host(host_name):
            
            host_name = to_text(host_name)
            if host_name in self._inventory.hosts:
                return self._inventory.hosts[host_name]
            else:
                return self._inventory.get_host(host_name)
        def search_handler_blocks_by_name(handler_name, handler_blocks):
            
            for handler_block in reversed(handler_blocks):
                for handler_task in handler_block.block:
                    if handler_task.name:
                        if not handler_task.cached_name:
                            if handler_templar.is_template(handler_task.name):
                                handler_templar.available_variables = self._variable_manager.get_vars(play=iterator._play,
                                                                                                      task=handler_task,
                                                                                                      _hosts=self._hosts_cache,
                                                                                                      _hosts_all=self._hosts_cache_all)