##### 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]
```

host_name = result.get('_ansible_delegated_vars', {}).get('ansible_delegated_host', None)
        return [host_name or task.delegate_to]
    def _set_always_delegated_facts(self, result, task):
        """Sets host facts for ``delegate_to`` hosts for facts that should
        always be delegated
        This operation mutates ``result`` to remove the always delegated facts
        See ``ALWAYS_DELEGATE_FACT_PREFIXES``
        """
        if task.delegate_to is None:
            return
        facts = result['ansible_facts']
        always_keys = set()
        _add = always_keys.add
        for fact_key in facts:
            for always_key in ALWAYS_DELEGATE_FACT_PREFIXES:
                if fact_key.startswith(always_key):
                    _add(fact_key)
        if always_keys:
            _pop = facts.pop
            always_facts = {
                'ansible_facts': dict((k, _pop(k)) for k in list(facts) if k in always_keys)
            }
            host_list = self.get_delegated_hosts(result, task)
            _set_host_facts = self._variable_manager.set_host_facts
            for target_host in host_list:
                _set_host_facts(target_host, always_facts)
    @debug_closure
    def _process_pending_results(self, iterator, one_pass=False, max_passes=None, do_handlers=False):