Enable gnocchi-metricd health check

This patch enables health check execution for gnocchi-metricd docker container.

Change-Id: I8717c56c35dc5a5ee7714ffaa48554ab7718035d
Depends-On: Ib82cb849540694106a869ec81694f1159967ee79
(cherry picked from commit 2415b5e1ec)

docker/services/gnocchi-metricd.yaml

@@ -117,6 +117,8 @@ outputs:
             net: host
             privileged: false
             restart: always
+            healthcheck:
+              test: /openstack/healthcheck
             volumes:
               list_concat:
                 - {get_attr: [ContainersCommon, volumes]}