commit 8efa88540635 (sch_sfq: avoid giving spurious NET_XMIT_CN signals)
forgot to call qdisc_tree_decrease_qlen() to signal upper levels that a
packet (from another flow) was dropped, leading to various problems.
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@29642 3c298f89-4303-0410-b956-a3cf2f4a3e73