Drop RpcProxy usage from oneconvergence plugin

This patch removes usage of the RpcProxy compatibility class from the
oneconvergence plugin.  The equivalent usage of oslo.messaging APIs is
now used intead.

Part of blueprint drop-rpc-compat.

Change-Id: Ifa74849ba9e3dc09cbb8cb3a723aeaa2b25b87ad
Drop RpcProxy usage from cisco apic ml2 plugin

Drop usage fo the RpcProxy compatibility class from the cisco apic ml2
plugin.  The equivalent oslo.messaging APIs are now used instead.

Part of blueprint drop-rpc-compat.

Change-Id: I415b65720a09652bae70fc1c1dada9f5727c4441
Remove unused xml constants

Change-Id: I38d720095a2fe703e55d895350e3894c35649d4e
Merge "Drop RpcProxy usage from oneconvergence plugin"
Merge "Drop RpcProxy usage from cisco apic ml2 plugin"
Merge "Remove unused xml constants"