integration: deleting the stack sometimes timeout

This increase a bit the timeout to let more time to heat to
cleanup the whole stack.

Change-Id: I8247ccef93f920c525739c5bf4ec1af217ec7fc8
diff --git a/ceilometer/tests/integration/gabbi/gabbits-live/autoscaling.yaml b/ceilometer/tests/integration/gabbi/gabbits-live/autoscaling.yaml
index 437d35d..52c3cde 100644
--- a/ceilometer/tests/integration/gabbi/gabbits-live/autoscaling.yaml
+++ b/ceilometer/tests/integration/gabbi/gabbits-live/autoscaling.yaml
@@ -156,7 +156,7 @@
       redirects: true
       method: GET
       poll:
-          count: 240
+          count: 300
           delay: 1
       status: 404