[qos] _validate_create_network_callback return in no network

It seems that _validate_create_network_callback notified without
network_id in payload, to avoid issues in such case return.

Change-Id: I15d22e0e2b4bf3e4f882b521bcd6a13f84e4feed
Closes-Bug: #2008912
(cherry picked from commit ec4bfb9)

Author: elajkat

neutron/services/qos/qos_plugin.py

@@ -610,9 +610,9 @@ def _validate_create_network_callback(self, resource, event, trigger,
         network_id = payload.resource_id
         network = network_object.Network.get_object(context, id=network_id)
 
-        policy_id = network.qos_policy_id
-        if policy_id is None:
+        if not network or not getattr(network, 'qos_policy_id', None):
             return
+        policy_id = network.qos_policy_id
 
         policy = policy_object.QosPolicy.get_object(
             context.elevated(), id=policy_id)