##### 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]
```

except KeyError:
                    iterator.get_next_task_for_host(self._inventory.get_host(host))
        
        
        failed_hosts = iterator.get_failed_hosts()
        unreachable_hosts = self._tqm._unreachable_hosts.keys()
        display.debug("running handlers")
        handler_result = self.run_handlers(iterator, play_context)
        if isinstance(handler_result, bool) and not handler_result:
            result |= self._tqm.RUN_ERROR
        elif not handler_result:
            result |= handler_result
        
        
        failed_hosts = set(failed_hosts).union(iterator.get_failed_hosts())
        unreachable_hosts = set(unreachable_hosts).union(self._tqm._unreachable_hosts.keys())
        
        if not isinstance(result, bool) and result != self._tqm.RUN_OK:
            return result
        elif len(unreachable_hosts) > 0:
            return self._tqm.RUN_UNREACHABLE_HOSTS
        elif len(failed_hosts) > 0:
            return self._tqm.RUN_FAILED_HOSTS
        else:
            return self._tqm.RUN_OK
    def get_hosts_remaining(self, play):
        self._set_hosts_cache(play, refresh=False)
        ignore = set(self._tqm._failed_hosts).union(self._tqm._unreachable_hosts)
        return [host for host in self._hosts_cache if host not in ignore]
    def get_failed_hosts(self, play):