Name plays in playbooks

In run_all, we start a bunch of plays in sequence, but it's difficult
to tell what they're doing until you see the tasks.  Name the plays
themselves to produce a better narrative structure.

Change-Id: I0597eab2c06c6963601dec689714c38101a4d470

playbooks/update-system-config.yaml

@@ -1,9 +1,8 @@
----
 - hosts: "localhost:!disabled"
+  name: "System-config: Update the system-config repo on bridge"
   connection: local
   gather_facts: false
   tasks:
-
     - name: Make sure system-config repo is up to date
       git:
         repo: https://git.openstack.org/openstack-infra/system-config