docker_logout: report change on successful logout (#60381)

* Mark logout as changed when docker logout does not return 'Not logged in to '.

* Add changelog.

* Improve logout detection.

* Also return output of 'docker logout'.

changelogs/fragments/60381-docker_login-logout-change.yml

@@ -0,0 +1,2 @@
+bugfixes:
+- "docker_login - report change on successful logout (https://github.com/ansible/ansible/issues/59232)"

lib/ansible/modules/cloud/docker/docker_login.py

@@ -224,6 +224,15 @@ class LoginManager(DockerBaseClass):
         (rc, out, err) = self.client.module.run_command(cmd)
         if rc != 0:
             self.fail("Could not log out: %s" % err)
+        if b'Not logged in to ' in out:
+            self.results['changed'] = False
+        elif b'Removing login credentials for ' in out:
+            self.results['changed'] = True
+        else:
+            self.client.module.warn('Unable to determine whether logout was successful.')
+
+        # Adding output to actions, so that user can inspect what was actually returned
+        self.results['actions'].append(to_text(out))
 
     def config_file_exists(self, path):
         if os.path.exists(path):