The notify "Restart keystone containers" is not correct

No handler named "Restart keystone containers", and we should restart
the keystone and the keystone-fernet container according to the context

Closes-Bug: #1699924

Change-Id: I62512dc022426cc762ff603d8554e48651fa621f

ansible/roles/keystone/tasks/config.yml

@@ -97,7 +97,8 @@
     - keystone_policy.stat.exists
   with_dict: "{{ keystone_services }}"
   notify:
-    - Restart keystone containers
+    - Restart keystone container
+    - Restart keystone-fernet container
 
 - name: Copying over wsgi-keystone.conf
   vars: