Add stable/wallaby jobs on master gate

We have stable/wallaby released so we should add
their job on master gate to keep branchless tempest
plugins compatible to stable branch.

Ref: Tempest plugins guide for stable branch testing:
- https://docs.openstack.org/tempest/latest/stable_branch_testing_policy.html

Change-Id: I493f44fdc7b5d4093e19ca19153644c20517941f

.zuul.yaml

@@ -11,6 +11,7 @@
         - nova-ceph-multistore:
             voting: false
         - cinder-tempest-plugin-cbak-ceph
+        - cinder-tempest-plugin-basic-wallaby
         - cinder-tempest-plugin-basic-victoria
         - cinder-tempest-plugin-basic-ussuri
         - cinder-tempest-plugin-basic-train
@@ -21,6 +22,7 @@
         - cinder-tempest-plugin-cbak-ceph
     experimental:
       jobs:
+        - cinder-tempest-plugin-cbak-ceph-wallaby
         - cinder-tempest-plugin-cbak-ceph-victoria
         - cinder-tempest-plugin-cbak-ceph-ussuri
         - cinder-tempest-plugin-cbak-ceph-train
@@ -106,6 +108,12 @@
       devstack_services:
         c-bak: true
 
+- job:
+    name: cinder-tempest-plugin-cbak-ceph-wallaby
+    parent: cinder-tempest-plugin-cbak-ceph
+    nodeset: openstack-single-node-focal
+    override-checkout: stable/wallaby
+
 - job:
     name: cinder-tempest-plugin-cbak-ceph-victoria
     parent: cinder-tempest-plugin-cbak-ceph
@@ -184,6 +192,12 @@
       - ^doc/.*$
       - ^releasenotes/.*$
 
+- job:
+    name: cinder-tempest-plugin-basic-wallaby
+    parent: cinder-tempest-plugin-basic
+    nodeset: openstack-single-node-focal
+    override-checkout: stable/wallaby
+
 - job:
     name: cinder-tempest-plugin-basic-victoria
     parent: cinder-tempest-plugin-basic