[NET_SCHED]: sch_htb: fix event cache time calculation

The event cache time must be an absolute value, when no event exists
it is incorrectly set to 1s instead of 1s in the future.
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/sched/sch_htb.c

@@ -976,8 +976,9 @@ static struct sk_buff *htb_dequeue(struct Qdisc *sch)
 
 		if (q->now >= q->near_ev_cache[level]) {
 			event = htb_do_events(q, level);
-			q->near_ev_cache[level] = event ? event :
-							  PSCHED_TICKS_PER_SEC;
+			if (!event)
+				event = q->now + PSCHED_TICKS_PER_SEC;
+			q->near_ev_cache[level] = event;
 		} else
 			event = q->near_ev_cache[level];