Fix setting custom dns

Related-Prod: PRODX-2063
Change-Id: I81ea10bf2bee52e39661a14eed179ef87dd27bf7
diff --git a/de/heat-templates/scripts/instance_boot.sh b/de/heat-templates/scripts/instance_boot.sh
index ab76dd0..54eed58 100644
--- a/de/heat-templates/scripts/instance_boot.sh
+++ b/de/heat-templates/scripts/instance_boot.sh
@@ -105,8 +105,9 @@
 [scheduling_configuration]
     enable_admin_ucp_scheduling = true
     default_node_orchestrator = \"kubernetes\"
-[cluster_config table]
-    dns = 172.18.208.44" | docker config create com.docker.ucp.config -
+[cluster_config]
+    dns = [\"172.18.208.44\"]
+" | docker config create com.docker.ucp.config -
 }
 
 function swarm_init {