use new payload objects for *_INIT callbacks

Part of the work we did while rehoming the callback modules introduced
the notion of payload objects [1] to replace the unstructured kwargs
used today. When using payloads event sources need to use publish()
rather than notify() to trigger the callback(s) and pass along a payload
object (if needed).

This patch begins to move us onto the payload objects by updating
BEFORE_INIT and AFTER_INIT event types to use the payloads.

Depends-On: I9194c7857f10392149159071cda8e080e93adc10

[1] https://github.com/openstack/neutron-lib/blob/master/doc/source/devref/callbacks.rst#event-payloads

Change-Id: I0485f4cf3c4eb9b0cbbe8245c48f322c0e807236

dragonflow/neutron/ml2/mech_driver.py

@@ -67,7 +67,7 @@ class DFMechDriver(api.MechanismDriver):
         self.subscribe_registries()
         df_qos.register()
 
-    def post_fork_initialize(self, resource, event, trigger, **kwargs):
+    def post_fork_initialize(self, resource, event, trigger, payload=None):
         # NOTE(nick-ma-z): This will initialize all workers (API, RPC,
         # plugin service, etc) and threads with network connections.
         self.nb_api = api_nb.NbApi.get_instance(True)

dragonflow/neutron/services/trunk/driver.py

@@ -49,13 +49,13 @@ class DfTrunkDriver(base.DriverBase, mixins.LazyNbApiMixin):
         except cfg.NoSuchOptError:
             return False
 
-    def register(self, resource, event, trigger, **kwargs):
+    def register(self, resource, event, trigger, payload=None):
         """
         Register the Dragonflow driver. This means registering to the
         add subport and delete subport events
         """
         super(DfTrunkDriver, self).register(resource, event, trigger,
-                                            **kwargs)
+                                            payload=payload)
         self._register_trunk_events()
         self._register_subport_events()