pkt_sched: HTB scheduler, change default hysteresis mode to off.

The HTB hysteresis mode reduce the CPU load, but at the
cost of scheduling accuracy.

On ADSL links (512 kbit/s upstream), this inaccuracy introduce
significant jitter, enought to disturbe VoIP.  For details see my
masters thesis (http://www.adsl-optimizer.dk/thesis/), chapter 7,
section 7.3.1, pp 69-70.
Signed-off-by: Jesper Dangaard Brouer <hawk@comx.dk>
Acked-by: Martin Devera <devik@cdi.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/sch_htb.c

@@ -53,7 +53,7 @@
 */
 
 #define HTB_HSIZE 16		/* classid hash size */
-#define HTB_HYSTERESIS 1	/* whether to use mode hysteresis for speedup */
+#define HTB_HYSTERESIS 0	/* whether to use mode hysteresis for speedup */
 #define HTB_VER 0x30011		/* major must be matched with number suplied by TC as version */
 
 #if HTB_VER >> 16 != TC_HTB_PROTOVER