Stop child objects changing status when LB locked

This patch corrects a bug in the load balancer locking that would
modify the child object provisioning status even though it is returning
that the load balancer is currently immutable.

Change-Id: I017bdcd902327d0cc363a6edb34c5eaeb9fd42e8
Story: 2001258
Task: 5788

octavia/db/repositories.py

@@ -269,6 +269,8 @@ class Repositories(object):
         # are changed.
         success = self.load_balancer.test_and_set_provisioning_status(
             session, lb_id, lb_prov_status)
+        if not success:
+            return success
         for listener_id in listener_ids:
             self.listener.update(session, listener_id,
                                  provisioning_status=listener_prov_status)