Rocky containers branchfull job

As tripleo-ci repo is branchless and has only master, we need
a rocky containers job that will run on this repo and will check
that we don't break anything for rocky containers building.
Breaking this job will affect periodic promotion because we started
to use this job for containers building in promotions.

Depends-On: https://review.openstack.org/#/c/648358
Change-Id: I8a1c69a9ab1de6992eb52b76862cacacaf265896

playbooks/tripleo-buildcontainers/run.yaml

@@ -28,6 +28,7 @@
     - name: Get contents of delorean repo baseurl for the version hash
       become: true
       shell: >
+        set -o pipefail &&
         cat /etc/yum.repos.d/delorean.repo |awk -F= '/baseurl/ {print $2}'
       register: baseurl
 

zuul.d/build-containers.yaml

@@ -7,11 +7,13 @@
     check:
       jobs:
         - tripleo-build-containers-centos-7
+        - tripleo-build-containers-centos-7-rocky
         - tripleo-build-containers-centos-7-buildah
     gate:
       queue: tripleo
       jobs:
         - tripleo-build-containers-centos-7
+        - tripleo-build-containers-centos-7-rocky
 
 - job:
     name: tripleo-build-containers-centos-7
@@ -19,6 +21,15 @@
     nodeset: single-centos-7-node
     voting: true
 
+- job:
+    name: tripleo-build-containers-centos-7-rocky
+    parent: tripleo-build-containers-base-with-files
+    nodeset: single-centos-7-node
+    override-checkout: stable/rocky
+    voting: true
+    vars:
+      branch_override: stable/rocky
+
 - job:
     name: tripleo-build-containers-centos-7-buildah
     parent: tripleo-build-containers-base-with-files