##### 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]
```

for target_host in host_list:
                                
                                
                                
                                
                                
                                if original_task.action != 'set_fact' or cacheable:
                                    self._variable_manager.set_host_facts(target_host, result_item['ansible_facts'].copy())
                                if original_task.action == 'set_fact':
                                    self._variable_manager.set_nonpersistent_facts(target_host, result_item['ansible_facts'].copy())
                    if 'ansible_stats' in result_item and 'data' in result_item['ansible_stats'] and result_item['ansible_stats']['data']:
                        if 'per_host' not in result_item['ansible_stats'] or result_item['ansible_stats']['per_host']:
                            host_list = self.get_task_hosts(iterator, original_host, original_task)
                        else:
                            host_list = [None]
                        data = result_item['ansible_stats']['data']
                        aggregate = 'aggregate' in result_item['ansible_stats'] and result_item['ansible_stats']['aggregate']
                        for myhost in host_list:
                            for k in data.keys():
                                if aggregate:
                                    self._tqm._stats.update_custom_stats(k, data[k], myhost)
                                else:
                                    self._tqm._stats.set_custom_stats(k, data[k], myhost)
                if 'diff' in task_result._result:
                    if self._diff or getattr(original_task, 'diff', False):
                        self._tqm.send_callback('v2_on_file_diff', task_result)
                if not isinstance(original_task, TaskInclude):
                    self._tqm._stats.increment('ok', original_host.name)
                    if 'changed' in task_result._result and task_result._result['changed']:
                        self._tqm._stats.increment('changed', original_host.name)