[pnfs] [PATCH 2.6-latest] Add partial backchannel support to the client

[ricardo.labiaga at netapp.com]

This patch set is the first part of the backchannel support for the client.
It's based on the existing 2.6.18 backchannel.  This initial part of the
functionality implements the detection of RPC calls over an existing connection
and queues them for processing by an NFSv4.1 backchannel RPC service.

The processing of the request and the reply to the server will be implemented
as a separate patch set.  Feedback welcome.

Thanks,

- ricardo