[watcher-tempest-plugin] Tag train-last

Train branch is in Extended Maintenance now[1]. Tempest and
tempest plugins are branchless which means master version of
Tempest and its plugins is used to test the supported stable
branches.

Once any stable branch is moved to EM state then, Tempest and
its plugins compatible tag[2] needs to be released so that we can
keep testing the EM stable branches with that tag once master
Tempest and its plugins are not compatible[3].

Tagging 'train-last'[4] as well as a new version also with same hash.

[1] https://releases.openstack.org/train/index.html
[2] https://docs.openstack.org/tempest/latest/stable_branch_support_policy.html
[3] https://docs.openstack.org/tempest/latest/tempest_and_plugins_compatible_version_policy.html
[4] https://docs.openstack.org/project-team-guide/stable-branches.html#extended-maintenance

Change-Id: I2f29a08bf785434c14cdaad1e2eda5230ba809cb

deliverables/train/watcher-tempest-plugin.yaml

@@ -13,3 +13,7 @@ releases:
     projects:
       - repo: openstack/watcher-tempest-plugin
         hash: 569bf8541ba0d2a18590045abae6080708e66aba
+  - version: train-last
+    projects:
+      - repo: openstack/watcher-tempest-plugin
+        hash: d97f4b3c36d2228da8278700bef8314af8b41689

deliverables/xena/watcher-tempest-plugin.yaml

@@ -9,3 +9,8 @@ repository-settings:
     tarball-base: watcher-tempest-plugin
 team: watcher
 type: tempest-plugin
+releases:
+  - version: 2.3.0
+    projects:
+      - repo: openstack/watcher-tempest-plugin
+        hash: d97f4b3c36d2228da8278700bef8314af8b41689