WIP: train => U

Author: jichenjc

.zuul/playbooks/run.yaml

@@ -25,7 +25,7 @@
     environment:
       USE_PYTHON3: 'True'
       DEVSTACK_GATE_LIBVIRT_TYPE: 'kvm'
-      OS_BRANCH: 'stable/train'
+      OS_BRANCH: 'stable/ussuri'
       OVERRIDE_ENABLED_SERVICES: 'dstat,etcd3,g-api,g-reg,key,mysql,n-api,n-api-meta,n-cond,n-cpu,n-novnc,n-sch,placement-api,q-agt,q-dhcp,q-l3,q-meta,q-metering,q-svc,rabbit'
   tasks:
   - name: Run kubernetes E2E conformance tests with ClusterAPI OpenStack