Add stable branch jobs on the plugins master gate

Supported stable branches in maintenance state
(ussuri, victoria, wallaby) use the Tempest and
plugin's master version for their testing.

To make sure master version (new tests or any changes)
are compatible with stable branch testing, we need to
add the stable branches job on the plugins master gate.
Tempest and many other plugins are already testing the
stable branches in same way [1].

Ussuri onwards, Tempest or plugins are py3 only, so we
are running only python3 version of stable jobs

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

[1] e8f1876aa6/.zuul.yaml (L646)

Change-Id: Ib1067db3771bacb287517e370c83a13d8bea89b5
Signed-off-by: Goutham Pacha Ravi <gouthampravi@gmail.com>

zuul.d/manila-tempest-stable-jobs.yaml

@@ -0,0 +1,19 @@
+# Stable branch jobs to test the trunk version of manila-tempest-plugin against
+# released stable branches of manila
+- job:
+    name: manila-tempest-plugin-lvm-wallaby
+    parent: manila-tempest-plugin-lvm
+    override-checkout: stable/wallaby
+    nodeset: openstack-single-node-focal
+
+- job:
+    name: manila-tempest-plugin-lvm-victoria
+    parent: manila-tempest-plugin-lvm
+    override-checkout: stable/victoria
+    nodeset: openstack-single-node-focal
+
+- job:
+    name: manila-tempest-plugin-lvm-ussuri
+    parent: manila-tempest-plugin-lvm
+    override-checkout: stable/ussuri
+    nodeset: openstack-single-node-bionic

zuul.d/project.yaml

@@ -7,6 +7,9 @@
         - manila-tempest-plugin-dummy-no-dhss
         - manila-tempest-plugin-dummy-dhss
         - manila-tempest-plugin-lvm
+        - manila-tempest-plugin-lvm-wallaby
+        - manila-tempest-plugin-lvm-victoria
+        - manila-tempest-plugin-lvm-ussuri
         - manila-tempest-plugin-zfsonlinux:
             voting: false
         - manila-tempest-plugin-cephfs-native: