Add "network_id" to "_after_router_interface_deleted" payload

This parameter, sent by the DHCP agent, is needed to remove the
workaround method "_get_network_lock_id".

The removal of this method will be done in [1] in Y release.

Related-Bug: #1732456

[1]https://review.opendev.org/c/openstack/neutron/+/800967

Change-Id: Ibd7fed33d314e901c69da33f42029f8ea67df98d

neutron/api/rpc/agentnotifiers/dhcp_rpc_agent_api.py

@@ -278,7 +278,8 @@ class DhcpAgentNotifyAPI(object):
                                         payload=None):
         port = payload.metadata.get('port')
         self._notify_agents(payload.context, 'port_delete_end',
-                            {'port_id': port['id']},
+                            {'port_id': port['id'],
+                             'network_id': port['network_id']},
                             port['network_id'])
 
     def _native_event_send_dhcp_notification(self, resource, event, trigger,