l2gw_callback triggered when not necessary

[Saverio Proto]

Running Openstack newton.

When a security group on any port on any tenant is updated in my Openstack deployment, a callback to the l2gw plugin triggers this stacktrace in the neutron server log file.

2017-11-30 10:22:45,911.911 17952 ERROR neutron.callbacks.manager Traceback (most recent call last):
2017-11-30 10:22:45,911.911 17952 ERROR neutron.callbacks.manager File "/usr/lib/python2.7/dist-packages/neutron/callbacks/manager.py", line 146, in _notify_loop
2017-11-30 10:22:45,911.911 17952 ERROR neutron.callbacks.manager callback(resource, event, trigger, **kwargs)
2017-11-30 10:22:45,911.911 17952 ERROR neutron.callbacks.manager File "/usr/lib/python2.7/dist-packages/networking_l2gw/db/l2gateway/l2gateway_db.py", line 555, in l2gw_callback
2017-11-30 10:22:45,911.911 17952 ERROR neutron.callbacks.manager l2gwservice.add_port_mac(context, port_dict)
2017-11-30 10:22:45,911.911 17952 ERROR neutron.callbacks.manager File "/usr/lib/python2.7/dist-packages/networking_l2gw/services/l2gateway/plugin.py", line 89, in add_port_mac
2017-11-30 10:22:45,911.911 17952 ERROR neutron.callbacks.manager self.driver.add_port_mac(context, port_dict)
2017-11-30 10:22:45,911.911 17952 ERROR neutron.callbacks.manager File "/usr/lib/python2.7/dist-packages/networking_l2gw/services/l2gateway/service_drivers/rpc_l2gw.py", line 103, in add_port_mac
2017-11-30 10:22:45,911.911 17952 ERROR neutron.callbacks.manager context, filters={'network_id': [network_id]}))
2017-11-30 10:22:45,911.911 17952 ERROR neutron.callbacks.manager File "/usr/lib/python2.7/dist-packages/networking_l2gw/db/l2gateway/l2gateway_db.py", line 317, in get_l2_gateway_connections
2017-11-30 10:22:45,911.911 17952 ERROR neutron.callbacks.manager self._admin_check(context, 'GET')
2017-11-30 10:22:45,911.911 17952 ERROR neutron.callbacks.manager File "/usr/lib/python2.7/dist-packages/networking_l2gw/db/l2gateway/l2gateway_db.py", line 348, in _admin_check
2017-11-30 10:22:45,911.911 17952 ERROR neutron.callbacks.manager raise exceptions.AdminRequired(reason=reason)
2017-11-30 10:22:45,911.911 17952 ERROR neutron.callbacks.manager AdminRequired: User does not have admin privileges: Cannot GET resource for non admin tenant.
2017-11-30 10:22:45,911.911 17952 ERROR neutron.callbacks.manager