CI: Run periodic stable jobs

Change-Id: If7854ce0f5fe8b90a9d06f3568aab53e4a51f8e5

Author: priteau

.zuul.yaml

@@ -187,6 +187,7 @@
       - check-requirements
       - openstack-cover-jobs
       - openstack-python3-jobs
+      - periodic-stable-jobs
       - publish-openstack-docs-pti
       - release-notes-jobs-python3
     check: