[storlets] Transition Ussuri to EM

This transition the ussuri 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: I4af8437dddabe2b2cfd81fd02380d9337dc305d8

deliverables/ussuri/storlets.yaml

@@ -17,6 +17,10 @@ releases:
       - repo: openstack/storlets
         hash: 3e8f98f4b6295d9b570be590368b1108181bbfeb
     diff-start: 4.0.0.0rc1
+  - version: ussuri-em
+    projects:
+      - repo: openstack/storlets
+        hash: 3e8f98f4b6295d9b570be590368b1108181bbfeb
 repository-settings:
   openstack/storlets: {}
 branches: