Pin ARA on devel job to stable branch

As noted in the linked thread, we need to stay on the stable branch
until we update various bits for the 1.0 version of ARA.  This should
fix the -devel job.

Change-Id: I3b5931cc9b8d55feb66971daed1ef28621da4b59

.zuul.yaml

@@ -389,6 +389,9 @@
       - name: github.com/philpep/testinfra
       - name: openstack/openstacksdk
       - name: recordsansible/ara
+        # NOTE(ianw): 2019-06-11 pinned to stable branch until we handle 1.0
+        #  http://lists.openstack.org/pipermail/openstack-infra/2019-June/006400.html
+        override-checkout: stable/0.x
     vars:
       bridge_ansible_name: '{{ ansible_user_dir}}/src/github.com/ansible/ansible'
       bridge_ansible_version: null