authorized_keys - consistent behavior in check_mode

Previously check_mode would incorrectly return changed=False even when a
change would have taken place if ran without check_mode, with
integration tests that confirmed this incorrect behavior. Also the
module did not correctly populate the return values when run in
check_mode. Both of these issues are resolved in this PR.

Fixes https://github.com/ansible-collections/ansible.posix/issues/37

Signed-off-by: Adam Miller <admiller@redhat.com>

plugins/modules/authorized_key.py

@@ -635,13 +635,9 @@ def enforce_state(module, params):
             }
             params['diff'] = diff
 
-        if module.check_mode:
-            module.exit_json(changed=True, diff=diff)
-        writefile(module, filename, new_content)
+        if not module.check_mode:
+            writefile(module, filename, new_content)
         params['changed'] = True
-    else:
-        if module.check_mode:
-            module.exit_json(changed=False)
 
     return params