Add osc repo to the base job definition

The osc-functional-devstack job is to be run against devstack changes in
order to verify that the devstack-tox-functional job, which our job is
based upon, doesn't introduce a regression[0]. In order to prevent this
from failing, include our own repo as required-project.

[0] https://review.openstack.org/526115

Change-Id: I782cd51dda1477c2e3a067cd902a3d3f29490083

.zuul.yaml

@@ -70,6 +70,8 @@
       - ^.*\.rst$
       - ^doc/.*$
       - ^releasenotes/.*$
+    required-projects:
+      - openstack/python-openstackclient
     vars:
       devstack_localrc:
         LIBS_FROM_GIT: python-openstackclient