Make broken tempest-full-py3-opensuse15 job only until stable/xena

tempest-full-py3-opensuse15 is failing all the time and
opensuse is not tested/supported distro in testing runtime
or devstack anymore. These job is removed from master gate
but it is in use until stable/xena.

- https://review.opendev.org/q/topic:%22remove-tempest-full-py3-opensuse15%22+(status:open%20OR%20status:merged)

Modifying it for until stable/xena only.

Change-Id: Ibe9166091011c08644cba783b7db77124cb17417

zuul.d/project.yaml

@@ -159,8 +159,6 @@
             irrelevant-files: *tempest-irrelevant-files
         - tempest-pg-full:
             irrelevant-files: *tempest-irrelevant-files
-        - tempest-full-py3-opensuse15:
-            irrelevant-files: *tempest-irrelevant-files
         - tempest-centos8-stream-fips:
             irrelevant-files: *tempest-irrelevant-files
     periodic-stable:

zuul.d/stable-jobs.yaml

@@ -178,3 +178,24 @@
       subnode:
         devstack_localrc:
           USE_PYTHON3: true
+
+- job:
+    name: tempest-full-py3-opensuse15
+    parent: tempest-full-py3
+    nodeset: devstack-single-node-opensuse-15
+    description: |
+      Base integration test with Neutron networking and py36 running
+      on openSUSE Leap 15.x
+    voting: false
+    # This job is not used after stable/xena and can be
+    # removed once stable/xena is EOL.
+    branches:
+      - stable/pike
+      - stable/queens
+      - stable/rocky
+      - stable/stein
+      - stable/train
+      - stable/ussuri
+      - stable/victoria
+      - stable/wallaby
+      - stable/xena

zuul.d/tempest-specific.yaml

@@ -68,15 +68,6 @@
         # without Swift, c-bak cannot run (in the Gate at least)
         c-bak: false
 
-- job:
-    name: tempest-full-py3-opensuse15
-    parent: tempest-full-py3
-    nodeset: devstack-single-node-opensuse-15
-    description: |
-      Base integration test with Neutron networking and py36 running
-      on openSUSE Leap 15.x
-    voting: false
-
 - job:
     name: tempest-full-py3-centos-8-stream
     parent: tempest-full-py3