[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 <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/sched/sch_generic.c

···
 	if (!ops->init || ops->init(sch, NULL) == 0)
 		return sch;
 
+	qdisc_destroy(sch);
 errout:
 	return NULL;
 }