netem: fix loss 4 state model

Patch from developers of the alternative loss models, downloaded from:
   http://netgroup.uniroma2.it/twiki/bin/view.cgi/Main/NetemCLG

 "In the case 1 of the switch statement in the if conditions we
   need to add clg->a4 to clg->a1, according to the model."
Signed-off-by: NStephen Hemminger <stephen@networkplumber.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/sched/sch_netem.c

@@ -215,10 +215,10 @@ static bool loss_4state(struct netem_sched_data *q)
 		if (rnd < clg->a4) {
 			clg->state = 4;
 			return true;
-		} else if (clg->a4 < rnd && rnd < clg->a1) {
+		} else if (clg->a4 < rnd && rnd < clg->a1 + clg->a4) {
 			clg->state = 3;
 			return true;
-		} else if (clg->a1 < rnd)
+		} else if (clg->a1 + clg->a4 < rnd)
 			clg->state = 1;
 
 		break;