Drop RpcProxy usage from ml2 AgentNotifierApi

Drop RpcProxy usage from ml2 AgentNotifierApi

Remove usage of the RpcProxy compatibility class from the ml2
AgentNotifierApi.  The equivalent oslo.messaging APIs are now used
instead.  A couple of other mixin APIs had to be converted at the same
time.

Note that there is one very minor functional change here.  The base
rpc version is set to '1.0' now instead of '1.1'.  The right pattern
to use is to always set the base to be N.0.  Any method that needs a
newer version should specify it.

Part of blueprint drop-rpc-compat.

Change-Id: I640568e2d73c9eb7a9505db640dc1427a1ae2abe