[ec2-api] Transition Train to EM

This transition the train 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: I95c1f916352e09d466f23eb104029bbf1f25754d

deliverables/train/ec2-api.yaml

@@ -20,6 +20,10 @@ releases:
     projects:
       - repo: openstack/ec2-api
         hash: f90157089654487af9a64fdbf73c76c6909c1bf3
+  - version: train-em
+    projects:
+      - repo: openstack/ec2-api
+        hash: f90157089654487af9a64fdbf73c76c6909c1bf3
 branches:
   - name: stable/train
     location: 9.0.0.0rc1