nfs41: Get the rpc_xprt * from the rpc_rqst instead of the rpc_clnt.

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: Rahul Iyer <iyer@netapp.com>
Signed-off-by: Ricardo Labiaga <ricardo.labiaga@netapp.com>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>

net/sunrpc/xprt.c

@@ -195,8 +195,8 @@ EXPORT_SYMBOL_GPL(xprt_load_transport);
  */
 int xprt_reserve_xprt(struct rpc_task *task)
 {
-	struct rpc_xprt	*xprt = task->tk_xprt;
 	struct rpc_rqst *req = task->tk_rqstp;
+	struct rpc_xprt	*xprt = req->rq_xprt;
 
 	if (test_and_set_bit(XPRT_LOCKED, &xprt->state)) {
 		if (task == xprt->snd_task)
@@ -858,7 +858,7 @@ int xprt_prepare_transmit(struct rpc_task *task)
 
 void xprt_end_transmit(struct rpc_task *task)
 {
-	xprt_release_write(task->tk_xprt, task);
+	xprt_release_write(task->tk_rqstp->rq_xprt, task);
 }
 
 /**