Add base support for update_port_bulk

As a complement to the create_port_bulk optimizations that took place in
the Stein cycle, create the ability to have an ML2 plugin optionally
expose an 'update_port_bulk' operation as well.  This will permit ML2
plugins to optimize this code path for bulk operations as well.

Change-Id: Id2c88a82715bccd1c23213828ef904322ab4386f

neutron/api/v2/base.py

@@ -674,7 +674,11 @@ class Controller(object):
             msg = _('The resource could not be found.')
             raise webob.exc.HTTPNotFound(msg)
 
-        obj_updater = getattr(self._plugin, action)
+        if self._native_bulk and hasattr(self._plugin, "%s_bulk" % action):
+            obj_updater = getattr(self._plugin, "%s_bulk" % action)
+        else:
+            obj_updater = getattr(self._plugin, action)
+
         kwargs = {self._resource: body}
         if parent_id:
             kwargs[self._parent_id_name] = parent_id