The neutron.common.rpc module has been in neutron-lib for awhile now and
neutron is shimmed to use neutron-lib already.
This patch removes neutron.common.rpc and switches the code over to use
neutron-lib's implementation where needed.
NeutronLibImpact
Change-Id: I733f07a8c4a2af071b3467bd710290eee11a4f4c