Add stable/liberty tripleo job

Recently tripleo created stable/liberty branches for several repos, ref
https://review.openstack.org/#/c/221811/, this adds an initial job
which will test using these new branches.

Co-Authored-By: Derek Higgins <derekh@redhat.com>
Depends-On: I34ea635382114bf4f075f3d8df1188c3beae8727
Depends-On: I1c7a696cf45f9b7d02d8f603fe3377769b1c5672
Change-Id: I5334525e16a8ff59aff48c8f8125ef27965aaba3

jenkins/jobs/projects.yaml

@@ -1971,31 +1971,44 @@
           type: 'nonha'
           node: 'tripleo-f21'
           trigger: 'gate'
+          branch-override: default
       - '{trigger}-tripleo-ci-{jobname}':
           jobname: 'f21-ha'
           type: 'ha'
           node: 'tripleo-f21'
           trigger: 'gate'
+          branch-override: default
       - '{trigger}-tripleo-ci-{jobname}':
           jobname: 'f21-ceph'
           type: 'ceph'
           node: 'tripleo-f21'
           trigger: 'gate'
+          branch-override: default
       - '{trigger}-tripleo-ci-{jobname}':
           jobname: 'f22-nonha'
           type: 'periodic-nonha'
           node: 'tripleo-f22'
           trigger: 'periodic'
+          branch-override: default
       - '{trigger}-tripleo-ci-{jobname}':
           jobname: 'f22-ha'
           type: 'periodic-ha'
           node: 'tripleo-f22'
           trigger: 'periodic'
+          branch-override: default
       - '{trigger}-tripleo-ci-{jobname}':
           jobname: 'f22-ceph'
           type: 'periodic-ceph'
           node: 'tripleo-f22'
           trigger: 'periodic'
+          branch-override: default
+      - '{trigger}-tripleo-ci-{jobname}':
+          jobname: 'f22-ha-liberty'
+          type: 'periodic-ha-liberty'
+          node: 'tripleo-f22'
+          trigger: 'periodic'
+          branch-override: stable/liberty
+
 
 - project:
     name: ironic-inspector

jenkins/jobs/tripleo.yaml

@@ -19,6 +19,11 @@
           export ZUUL_BRANCH=${{ZUUL_BRANCH:-master}}
           export ZUUL_REF=${{ZUUL_REF:-None}}
 
+          export BRANCH_OVERRIDE={branch-override}
+          if [ "$BRANCH_OVERRIDE" != "default" ] ; then
+              export OVERRIDE_ZUUL_BRANCH=$BRANCH_OVERRIDE
+          fi
+
           export PYTHONUNBUFFERED=true
           export DEVSTACK_GATE_TIMEOUT=170
           export DEVSTACK_GATE_TEMPEST=0

zuul/layout.yaml

@@ -3437,6 +3437,7 @@ projects:
       - periodic-tripleo-ci-f22-ceph
       - periodic-tripleo-ci-f22-ha
       - periodic-tripleo-ci-f22-nonha
+      - periodic-tripleo-ci-f22-ha-liberty
 
   - name: openstack-infra/trystack-site
     template: