Wait until stack deletion is completed at test cleanup

Some faults tests are not stable because stack deletion is not completed during
the cleanup of the previous tests
Sometimes the disruption of the next test is executed while the stack
deletion is in progress and due to this the stack remains in state
delete in progress forever

Change-Id: I07f1e21d89174cfeaca77a93bfa8772a757b1afb

tobiko/openstack/heat/_stack.py

@@ -217,6 +217,8 @@ class HeatStackFixture(tobiko.SharedFixture):
 
     def cleanup_stack(self):
         self.delete_stack()
+        if self.stack:
+            self.wait_for_delete_complete()
 
     def delete_stack(self, stack_id=None):
         """Deletes stack."""