[Queens only] Clean yum metadata.

Clean yum metadata before run the check update for docker. Currently the
overcloud update run doesn't return an error even if not able to connect
to yum repository. Check the bugzilla[1] to have more information.

[1] https://bugzilla.redhat.com/show_bug.cgi?id=1822576

Change-Id: I9e0099ff39d39c4d4c5f96db590e73d538ed241b

puppet/services/docker.yaml

@@ -151,6 +151,8 @@ outputs:
               awk -F ":" '/Out of sync:/ { print $2}'
             register: puppet_docker_noop_output
             failed_when: false
+          - name: Clean yum metadata
+            shell: yum clean metadata
           - name: Is docker going to be updated
             shell: yum check-update docker
             register: docker_check_update