Fix documentation for kolla_docker image pulling

The example to pull images is incorrect, this patch
addresses it and corrects it accordingly.

Change-Id: Ice79e7f73d99c024781cb379d190f6d05e1a34a9

ansible/library/kolla_docker.py

@@ -180,7 +180,7 @@ EXAMPLES = '''
         action: remove_container
     - name: Pull image without starting container
       kolla_docker:
-        action: pull_container
+        action: pull_image
         image: private-registry.example.com:5000/ubuntu
     - name: Create named volume
         action: create_volume