Enable nova-migration-target health check

This patch enables health check execution for nova-migration-target
docker container. Nova compute image is used for this container
and support for this service has been implemented in previous release
already.

Change-Id: I2bf04544d4cf200ce7e3960a7c71ab15f013fe52
Depends-On: Ib82cb849540694106a869ec81694f1159967ee79

docker/services/nova-migration-target.yaml

@@ -140,6 +140,8 @@ outputs:
             privileged: true
             user: root
             restart: always
+            healthcheck:
+              test: /openstack/healthcheck
             volumes:
               list_concat:
                 - {get_attr: [ContainersCommon, volumes]}