Add healthcheck script for gnocchi-metricd

This patch adds script for docker health check of gnocchi-metricd service.
The script checks existance of service with opened connections to Redis.

Change-Id: Icbf450a797f95fb5966005295bd33975077e4aa5

healthcheck/gnocchi-metricd

@@ -0,0 +1,14 @@
+#!/bin/bash
+
+. ${HEALTHCHECK_SCRIPTS:-/usr/share/openstack-tripleo-common/healthcheck}/common.sh
+
+process='gnocchi-metricd'
+args="${@:-6379}"
+
+if healthcheck_port $process $args; then
+  exit 0
+else
+  ports=${args// /,}
+  echo "There is no $process process with opened Redis ports ($ports) running in the container"
+  exit 1
+fi