Fixed testing of existing stacks

Change-Id: If3a8e9611768833acc3a0140e76aec12bb4b7005
diff --git a/src/com/mirantis/mk/Openstack.groovy b/src/com/mirantis/mk/Openstack.groovy
index 36b16ca..5827ebb 100644
--- a/src/com/mirantis/mk/Openstack.groovy
+++ b/src/com/mirantis/mk/Openstack.groovy
@@ -195,7 +195,7 @@
  * @param path         Optional path to the custom virtualenv
  */
 def getStacksForNameContains(client, filter, path = null){
-    cmd = 'heat stack-list | awk \'NR>3 {print $4}\' | sed \'$ d\' | grep ' + filter
+    cmd = 'heat stack-list | awk \'NR>3 {print $4}\' | sed \'$ d\' | grep ' + filter + '|| true'
     return runOpenstackCommand(cmd, client, path).trim().tokenize("\n")
 }