[Puppet OpenStack] Transition Stein to EM

This transition the stein branch to extended maintenance.
Changes for bugfixes and things the team deems important are
still encouraged, but there will no longer be official releases
off of the branch.

Please +1 if the team is ready for us to proceed with this
transition, or -1 if there are any final backports currently in
flight that we should wait for. For the latter case, please
update the patch with the new commit hash after doing a final
release to get those changes out so we know to proceed with the
transition.

Change-Id: Icdd4a7b14f35ee51b614e530f05ace76dfad4665

deliverables/stein/puppet-mistral.yaml

@@ -22,6 +22,10 @@ releases:
       - hash: 3d4b52146f2cac719d058c4d31d11a84b6f5abd5
         repo: openstack/puppet-mistral
     version: 14.4.0
+  - version: stein-em
+    projects:
+      - repo: openstack/puppet-mistral
+        hash: 3d4b52146f2cac719d058c4d31d11a84b6f5abd5
 branches:
   - location: 14.4.0
     name: stable/stein