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:

"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.
"

Depends-On: I3214045856d0bbd05a0000eeafb769e4697cd34c

Change-Id: I375f54225773769de422c3a3cbe3496febee9b86

cinder/rpc.py

@@ -29,6 +29,7 @@ __all__ = [
 from oslo_config import cfg
 from oslo_log import log as logging
 import oslo_messaging as messaging
+from oslo_messaging.rpc import dispatcher
 from oslo_utils import importutils
 profiler = importutils.try_import('osprofiler.profiler')
 import six
@@ -164,11 +165,13 @@ def get_client(target, version_cap=None, serializer=None):
 def get_server(target, endpoints, serializer=None):
     assert TRANSPORT is not None
     serializer = RequestContextSerializer(serializer)
+    access_policy = dispatcher.DefaultRPCAccessPolicy
     return messaging.get_rpc_server(TRANSPORT,
                                     target,
                                     endpoints,
                                     executor='eventlet',
-                                    serializer=serializer)
+                                    serializer=serializer,
+                                    access_policy=access_policy)
 
 
 @utils.if_notifications_enabled