Enable mistral-event-engine health check

This patch enables health check execution for mistral-event-engine
docker container.

Change-Id: I804da516d5fe335a0a050ce3aa3c6a44c2be9f59
Depends-On: I074f7911e8a41d45249dbbf277138bc80ee3a774

docker/services/mistral-event-engine.yaml

@@ -96,6 +96,8 @@ outputs:
             net: host
             privileged: false
             restart: always
+            healthcheck:
+              test: /openstack/healthcheck
             volumes:
               list_concat:
                 - {get_attr: [ContainersCommon, volumes]}