[ec2-api] 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: I2b4a7a73b0280ae94c39205519bf25e2723121f0

deliverables/ussuri/ec2-api.yaml

@@ -16,6 +16,10 @@ releases:
       - repo: openstack/ec2-api
         hash: 21c15aa680caabf3587627dd900469d77d13d9ae
     diff-start: 9.0.0
+  - version: ussuri-em
+    projects:
+      - repo: openstack/ec2-api
+        hash: 21c15aa680caabf3587627dd900469d77d13d9ae
 branches:
   - name: stable/ussuri
     location: 10.0.0.0rc1