Fix join node command

Related-Prod: PRODX-0000
Change-Id: I7b00d9f37c3ddb3e2a5153f867f2b2071d281ba7
diff --git a/de/heat-templates/scripts/instance_boot.sh b/de/heat-templates/scripts/instance_boot.sh
index f3ee628..4936aaf 100644
--- a/de/heat-templates/scripts/instance_boot.sh
+++ b/de/heat-templates/scripts/instance_boot.sh
@@ -195,7 +195,8 @@
 function join_node {
     local type=${1}
     function retry_join_node {
-        docker swarm join-token $type
+        cmd=$(docker swarm join-token $type |grep 'docker swarm join')
+        $cmd
     }
     retry 10 "Failed to join node to swarm" retry_join_node
 }