docker_image: Fix idempotency of pull (#31956)

when pulling an image with force=yes the task was marked as changed
everytime even when the image hasn't changed.

This was due to a bad comparison of the image tag before the pull
and after the pull.

Fixes #22596

Signed-off-by: Alberto Murillo <albertomurillosilva@gmail.com>

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

@@ -336,8 +336,8 @@ class ImageManager(DockerBaseClass):
                 self.results['actions'].append('Pulled image %s:%s' % (self.name, self.tag))
                 self.results['changed'] = True
                 if not self.check_mode:
-                    self.results['image'] = self.client.pull_image(self.name, tag=self.tag)
-                    if image and image == self.results['image']:
+                    self.results['image'], already_latest = self.client.pull_image(self.name, tag=self.tag)
+                    if already_latest:
                         self.results['changed'] = False
 
         if self.archive_path: