Add stable branch tests for centos-8s tempest tests

Add a variation of the telemetry-dsvm-integration-centos-8s jobs using
branch selectors and provide a config for python 3.6 on older branches
(i.e. pre-yoga)

Change-Id: Ia57b83c7d764e2bb4eda19a46034ff2d3353aff7

.zuul.yaml

@@ -147,14 +147,26 @@
     name: telemetry-dsvm-integration-centos-8s
     nodeset: devstack-single-node-centos-8-stream
     parent: telemetry-dsvm-integration
+    branches:
+      - stable/wallaby
+      - stable/xena
+      - stable/yoga
     description: |
-      Telemetry devstack tempest tests job for a Centos 8 stream system
+      Telemetry devstack tempest test job for Centos 8 stream system using python 36
+      i.e. yoga and below
+    vars:
+      devstack_localrc:
+        # for versions of devstack that don't explicitly support rhel8
+        FORCE: 'yes'
+        TEMPEST_BRANCH: '30.1.0'
+        TEMPEST_VENV_UPPER_CONSTRAINTS: '/opt/stack/requirements/upper-constraints.txt'
 
 - job:
     name: telemetry-dsvm-integration-centos-8s-fips
     parent: telemetry-dsvm-integration-centos-8s
     description: |
-      Telemetry devstack tempest tests job for a FIPS enabled Centos 8 stream system
+      Telemetry devstack tempest tests job for a FIPS enabled Centos 8 stream system using python36
+      i.e. yoga and below
     pre-run: playbooks/enable-fips.yaml
     vars:
       nslookup_target: 'opendev.org'