fix typho in Aws class waitForStatus

Change-Id: Ic27562d3bd1e23752c00456342dae4cf1078eb43
diff --git a/src/com/mirantis/mk/Aws.groovy b/src/com/mirantis/mk/Aws.groovy
index 113033d..56c5ecc 100644
--- a/src/com/mirantis/mk/Aws.groovy
+++ b/src/com/mirantis/mk/Aws.groovy
@@ -94,7 +94,7 @@
                 }
 
                 // check for failed state
-                if (stack_failed.contains(stack_info['StackStatus'])) {
+                if (state_failed.contains(stack_info['StackStatus'])) {
                     throw new Exception("Stack ${stack_name} in in failed state")
                 }