sunrpc: fix loss of task->tk_status after rpc_delay call in xprt_alloc_slot

xprt_alloc_slot will call rpc_delay() to make the task wait a bit before
retrying when it gets back an -ENOMEM error from xprt_dynamic_alloc_slot.
The problem is that rpc_delay will clear the task->tk_status, causing
call_reserveresult to abort the task.

The solution is simply to let call_reserveresult handle the ENOMEM error
directly.

Reported-by: Jeff Layton <jlayton@redhat.com>
Cc: stable@vger.kernel.org [>= 3.1]
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index adf2990..25302c8 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -1288,6 +1288,8 @@
 	}
 
 	switch (status) {
+	case -ENOMEM:
+		rpc_delay(task, HZ >> 2);
 	case -EAGAIN:	/* woken up; retry */
 		task->tk_action = call_reserve;
 		return;