netem: fix dequeue

commit 50612537 (netem: fix classful handling) added two errors in
netem_dequeue()

1) After checking skb at the head of tfifo queue for time constraints,
   it dequeues tail skb, thus adding unwanted reordering.

2) qdisc stats are updated twice per packet
   (one when packet dequeued from tfifo, once when delivered)
Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/sched/sch_netem.c

@@ -501,9 +501,8 @@ static struct sk_buff *netem_dequeue(struct Qdisc *sch)
 
 		/* if more time remaining? */
 		if (cb->time_to_send <= psched_get_time()) {
-			skb = qdisc_dequeue_tail(sch);
-			if (unlikely(!skb))
-				goto qdisc_dequeue;
+			__skb_unlink(skb, &sch->q);
+			sch->qstats.backlog -= qdisc_pkt_len(skb);
 
 #ifdef CONFIG_NET_CLS_ACT
 			/*
@@ -539,7 +538,6 @@ static struct sk_buff *netem_dequeue(struct Qdisc *sch)
 		qdisc_watchdog_schedule(&q->watchdog, cb->time_to_send);
 	}
 
-qdisc_dequeue:
 	if (q->qdisc) {
 		skb = q->qdisc->ops->dequeue(q->qdisc);
 		if (skb)