Set access_policy for messaging's dispatcher

oslo.messaging allow dispatcher to restrict endpoint methods
since 5.11.0 in d3a8f280ebd6fd12865fd20c4d772774e39aefa2, set with
DefaultRPCAccessPolicy to fix FutureWarning like:

FutureWarning: The access_policy argument is changing its default
value to <class 'oslo_messaging.rpc.dispatcher.DefaultRPCAccessPolicy'>
in version '?', please update the code to explicitly set None as the
value: access_policy defaults to LegacyRPCAccessPolicy which exposes
private methods. Explicitly set access_policy to DefaultRPCAccessPolicy
or ExplicitRPCAccessPolicy.

Change-Id: Iacb22af0836ead11043f6852fa17c6e024311a3c

manila/rpc.py

@@ -27,6 +27,7 @@ __all__ = [
 
 from oslo_config import cfg
 import oslo_messaging as messaging
+from oslo_messaging.rpc import dispatcher
 from oslo_serialization import jsonutils
 
 import manila.context
@@ -123,12 +124,14 @@ def get_client(target, version_cap=None, serializer=None):
 
 def get_server(target, endpoints, serializer=None):
     assert TRANSPORT is not None
+    access_policy = dispatcher.DefaultRPCAccessPolicy
     serializer = RequestContextSerializer(serializer)
     return messaging.get_rpc_server(TRANSPORT,
                                     target,
                                     endpoints,
                                     executor='eventlet',
-                                    serializer=serializer)
+                                    serializer=serializer,
+                                    access_policy=access_policy)
 
 
 def get_notifier(service=None, host=None, publisher_id=None):