Add healthcheck script for Mistral event-engine

This patch adds a script for docker health check of Mistral's
event-engine service. The script checks existence of service with open
connections to RabbitMQ.

Change-Id: I074f7911e8a41d45249dbbf277138bc80ee3a774

healthcheck/mistral-event-engine

@@ -0,0 +1,14 @@
+#!/bin/bash
+
+. ${HEALTHCHECK_SCRIPTS:-/usr/share/openstack-tripleo-common/healthcheck}/common.sh
+
+process='mistral-server'
+args="${@:-5671 5672}"
+
+if healthcheck_port $process $args; then
+  exit 0
+else
+  ports=${args// /,}
+  echo "There is no $process process with opened RabbitMQ ports ($ports) running in the container"
+  exit 1
+fi