RPC: Don't kill timers when calling rpc_restart_call() after rpc_delay()

 Currently, if we restart an RPC call after having set an RPC delay (for
 instance in the case where an NFS EJUKEBOX error has occurred) the call
 to rpc_delete_timer() at the top of the rpc_execute() loop will
 kill off our timer.

 This patch causes rpc_delete_timer() to detect if the rpc_task is still
 queued on a wait queue, and refuse to delete the timer if this is the case.

 Problem diagnosed by Jan Sanislo and Olaf Kirch.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

net/sunrpc/sched.c

@@ -132,9 +132,11 @@ __rpc_add_timer(struct rpc_task *task, rpc_action timer)
  * Delete any timer for the current task. Because we use del_timer_sync(),
  * this function should never be called while holding queue->lock.
  */
-static inline void
+static void
 rpc_delete_timer(struct rpc_task *task)
 {
+	if (RPC_IS_QUEUED(task))
+		return;
 	if (test_and_clear_bit(RPC_TASK_HAS_TIMER, &task->tk_runstate)) {
 		del_singleshot_timer_sync(&task->tk_timer);
 		dprintk("RPC: %4d deleting timer\n", task->tk_pid);