Obtain the rpc_xprt from the rpc_rqst so that calls and callback replies
can both use the same code path.  A client needs the rpc_xprt in order
to reply to a callback.
Signed-off-by: NRahul Iyer <iyer@netapp.com>
Signed-off-by: NRicardo Labiaga <ricardo.labiaga@netapp.com>
Signed-off-by: NBenny Halevy <bhalevy@panasas.com>