Add stable/zed jobs on master gate

As zed is released, we should add its 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: I2f81f1801f8f7a049a6fc012c8e9455adceeb9ec

.zuul.yaml

@@ -8,6 +8,8 @@
       jobs:
         - vitrage-tempest-plugin-api
         - vitrage-tempest-plugin-datasources
+        - vitrage-tempest-plugin-datasources-zed
+        - vitrage-tempest-plugin-api-zed
         - vitrage-tempest-plugin-datasources-yoga
         - vitrage-tempest-plugin-api-yoga
         - vitrage-tempest-plugin-datasources-xena:
@@ -227,6 +229,18 @@
       devstack_plugins:
         vitrage: https://opendev.org/openstack/vitrage
 
+- job:
+    name: vitrage-tempest-plugin-api-zed
+    parent: vitrage-tempest-plugin-api
+    nodeset: openstack-single-node-focal
+    override-checkout: stable/zed
+
+- job:
+    name: vitrage-tempest-plugin-datasources-zed
+    parent: vitrage-tempest-plugin-datasources
+    nodeset: openstack-single-node-focal
+    override-checkout: stable/zed
+
 - job:
     name: vitrage-tempest-plugin-api-yoga
     parent: vitrage-tempest-plugin-api