Stop oslo_messaging from error logging CallbackNotFound

This is expected when the server is pushing for a resource
and some listeners (like the OVS agent) are not interested
in the event. This happens when Trunk create/delete events
are dispatched by the server.

Change-Id: I90ddffda546af45ca85b3e4f4f22eed005d971df
Closes-bug: #1625872

neutron/api/rpc/handlers/resources_rpc.py

@@ -252,6 +252,7 @@ class ResourcesPushRpcCallback(object):
     target = oslo_messaging.Target(version='1.1',
                                    namespace=constants.RPC_NAMESPACE_RESOURCES)
 
+    @oslo_messaging.expected_exceptions(rpc_exc.CallbackNotFound)
     def push(self, context, **kwargs):
         """Push receiver, will always receive resources of the same type."""
         # TODO(mangelajo): accept single 'resource' parameter for backwards