[train][goal] Define new 'qinling-tempest-ipv6-only' job in gate

As part of Train community goal 'Support IPv6-Only Deployments and Testing'[1],
Tempest has defined the base job 'devstack-tempest-ipv6' (adding
in Depends-On patch) which will deploy services on IPv6.

This commit adds the new job 'qinling-tempest-ipv6-only'
run on gate which is derived from 'devstack-tempest-ipv6'.

Verification structure will be:
- 'devstack-IPv6' deploy the service on IPv6
- 'devstack-tempest-ipv6' run will verify the IPv6-only setting and listen address
- 'qinling-tempest-ipv6-only' will run the tests.

Story: #2005477
Task: #35922

[1] https://governance.openstack.org/tc/goals/train/ipv6-support-and-testing.html

Change-Id: Ib223233c43db58db8d7762a32e48029c8ff6f5db

.zuul.yaml

@@ -2,12 +2,12 @@
     name: qinling-tempest
     parent: devstack-tempest
     timeout: 7800
-    required-projects:
+    required-projects: &base_required_projects
       - openstack/devstack-gate
       - openstack/python-qinlingclient
       - openstack/qinling
       - openstack/tempest
-    irrelevant-files:
+    irrelevant-files: &base_irrelevant_files
       - ^.*\.rst$
       - ^doc/.*
       - ^qinling/tests/unit/.*$
@@ -15,7 +15,7 @@
       - ^api-ref/.*$
     pre-run: playbooks/pre.yaml
     post-run: playbooks/post.yaml
-    vars:
+    vars: &base_vars
       devstack_services:
         # Disable unneeded services.
         # These services are enabled in the devstack base job and are not
@@ -60,6 +60,16 @@
       # "Not enough workers available" error.
       tempest_concurrency: 2
 
+- job:
+    name: qinling-tempest-ipv6-only
+    parent: devstack-tempest-ipv6
+    description: |
+      Qinling devstack tempest tests job for IPv6-only deployment
+    timeout: 7800
+    irrelevant-files: *base_irrelevant_files
+    required-projects: *base_required_projects
+    vars: *base_vars
+
 - job:
     name: qinling-tempest-centos7
     parent: qinling-tempest
@@ -77,10 +87,12 @@
     check:
       jobs:
         - qinling-tempest
+        - qinling-tempest-ipv6-only
     gate:
       queue: qinling
       jobs:
         - qinling-tempest
+        - qinling-tempest-ipv6-only
     experimental:
       jobs:
         - qinling-tempest-centos7