Updated openstack/openstack
Project: openstack/neutron  a3f95736cb1b115ceb3611daaa6d5162aca0cfd7

Remove RpcCallback class

All users of the RpcCallback class have been converted to directly
define the oslo.messaging Target so this compatibility class is no
longer needed.

This is the final change of blueprint drop-rpc-compat.

Change-Id: I25474569850f3f2c176e7eee7aafa7ff0180b809