[PKT_SCHED]: Fix missing qdisc_destroy() in qdisc_create_dflt()

qdisc_create_dflt() is missing to destroy the newly allocated
default qdisc if the initialization fails resulting in leaks
of all kinds. The only caller in mainline which may trigger
this bug is sch_tbf.c in tbf_create_dflt_qdisc().

Note: qdisc_create_dflt() doesn't fulfill the official locking
      requirements of qdisc_destroy() but since the qdisc could
      never be seen by the outside world this doesn't matter
      and it can stay as-is until the locking of pkt_sched
      is cleaned up.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/sch_generic.c

@@ -438,6 +438,7 @@ struct Qdisc * qdisc_create_dflt(struct net_device *dev, struct Qdisc_ops *ops)
 	if (!ops->init || ops->init(sch, NULL) == 0)
 		return sch;
 
+	qdisc_destroy(sch);
 errout:
 	return NULL;
 }