Elasticsearch: kill process after data node drain

This updates the Elasticsearch entrypoint override for the data
nodes to include a signal to kill the process after the trap to
drain each data node completes

Change-Id: Iccd4342fe16d06787cb24342d9a57e4de12e6980

elasticsearch/templates/bin/_elasticsearch.sh.tpl

@@ -66,6 +66,7 @@ function start_data_node () {
       sleep 5
     done
     echo "Node ${NODE_NAME} is ready to shutdown"
+    kill -TERM 1
   }
   trap drain_data_node TERM EXIT HUP INT
   wait