Finalize support for setting up RPC client transports to remote RPC
services addressed via IPv6.

Based on work done by Gilles Quillard at Bull Open Source.
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Cc: Aurelien Charbon <aurelien.charbon@ext.bull.net>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>