Wait for stack status instead of group status

SUSPEND happens in reverse order, so waiting for the group to reach
SUSPEND_COMPLETE/SUSPEND_FAILED would result in timeout, if SUSPEND
for the policy resource fails.

Change-Id: Ie690d49734d164554ee6cf6c11f8c45a2832a8fe
Related-Bug: #1595819
diff --git a/functional/test_autoscaling.py b/functional/test_autoscaling.py
index ebc7f61..e97ae89 100644
--- a/functional/test_autoscaling.py
+++ b/functional/test_autoscaling.py
@@ -726,8 +726,9 @@
 
         # suspend the top level stack.
         self.client.actions.suspend(stack_id=stack_identifier)
-        self._wait_for_resource_status(
-            stack_identifier, 'JobServerGroup', 'SUSPEND_COMPLETE')
+
+        # Wait for stack to reach SUSPEND_COMPLETE
+        self._wait_for_stack_status(stack_identifier, 'SUSPEND_COMPLETE')
 
         # Send a signal and an exception will raise
         ex = self.assertRaises(exc.BadRequest,