Drop RpcProxy usage from ibm plugin
Drop RpcProxy usage from ibm plugin

Drop usage of the RpcProxy compatibility class from the ibm plugin.
Direct usage of oslo.messaging APIs is now done instead.

Part of blueprint drop-rpc-compat.

Change-Id: I3163d0a5e5f042c02e83995e84eb962e002f27cb

gkotton/vmware-nsx,gkotton/vmware-nsx