fixes-3.14: remove useless warning

debloat script causes warning on changing qdisc for inactive
interface. I don't like that.

[  +0.843777] ------------[ cut here ]------------
[  +0.000014] WARNING: CPU: 2 PID: 1939 at net/sched/sch_api.c:279 qdisc_list_add+0x6e/0x80()
[  +0.000003] Modules linked in: uvcvideo videobuf2_vmalloc videobuf2_memops videobuf2_core videodev media ath3k btusb bluetooth 6lowpan_iphc
xt_conn
track iptable_filter xt_TCPMSS xt_tcpudp iptable_mangle ipt_MASQUERADE iptable_nat bridge stp llc nf_conntrack_ipv4 nf_defrag_ipv4
nf_nat_ipv4 nf_nat
 nf_conntrack ip_tables x_tables x86_pkg_temp_thermal intel_powerclamp crct10dif_pclmul crc32_pclmul nls_cp437 vfat fat crc32c_intel dell_wmi
sparse_
keymap iTCO_wdt iTCO_vendor_support ghash_clmulni_intel aesni_intel aes_x86_64 lrw gf128mul glue_helper ablk_helper cryptd dell_laptop dcdbas
wmi arc
4 evdev microcode psmouse(O) serio_raw lpc_ich mfd_core snd_hda_codec_hdmi alx mdio i2c_i801 ath9k ath9k_common ath9k_hw ath mac80211
cfg80211 rfkill
 snd_hda_codec_cirrus snd_hda_codec_generic snd_hda_intel snd_hda_codec
[  +0.000082]  snd_hwdep snd_pcm snd_timer snd soundcore tcp_yeah tcp_vegas msr kvm_intel kvm autofs4 efivarfs sd_mod crc_t10dif
crct10dif_common ehc
i_pci xhci_hcd ehci_hcd ahci libahci libata scsi_mod usbcore usb_common
[  +0.000031] CPU: 2 PID: 1939 Comm: tc Tainted: G           O 3.14.0-pf1 #1
[  +0.000003] Hardware name: Dell Inc.          Vostro 3360/0F5DWF, BIOS A18 09/25/2013
[  +0.000003]  0000000000000009 ffff880422689948 ffffffff815dfd7f 0000000000000000
[  +0.000007]  ffff880422689980 ffffffff8105e72d ffff880426834a00 ffffffff81aa6e80
[  +0.000006]  ffff88042739e000 ffff880426835000 ffff88042739e000 ffff880422689990
[  +0.000005] Call Trace:
[  +0.000009]  [<ffffffff815dfd7f>] dump_stack+0x4d/0x6f
[  +0.000007]  [<ffffffff8105e72d>] warn_slowpath_common+0x7d/0xa0
[  +0.000006]  [<ffffffff8105e80a>] warn_slowpath_null+0x1a/0x20
[  +0.000005]  [<ffffffff8151e4de>] qdisc_list_add+0x6e/0x80
[  +0.000005]  [<ffffffff8151cac7>] mq_attach+0x77/0xa0
[  +0.000006]  [<ffffffff8151e1cf>] qdisc_graft+0x15f/0x2b0
[  +0.000006]  [<ffffffff8151fd34>] tc_modify_qdisc+0x4c4/0x580
[  +0.000006]  [<ffffffff8150a2a9>] rtnetlink_rcv_msg+0x99/0x260
[  +0.000006]  [<ffffffff814ea96e>] ? __alloc_skb+0x7e/0x1d0
[  +0.000004]  [<ffffffff8150a210>] ? rtnetlink_rcv+0x30/0x30
[  +0.000006]  [<ffffffff81528c39>] netlink_rcv_skb+0xa9/0xc0
[  +0.000004]  [<ffffffff8150a208>] rtnetlink_rcv+0x28/0x30
[  +0.000005]  [<ffffffff81528198>] netlink_unicast+0xe8/0x1c0
[  +0.000005]  [<ffffffff81528679>] netlink_sendmsg+0x359/0x760
[  +0.000005]  [<ffffffff81525ea4>] ? netlink_rcv_wake+0x44/0x60
[  +0.000006]  [<ffffffff8129c4b4>] ? tomoyo_socket_sendmsg_permission+0x24/0xb0
[  +0.000006]  [<ffffffff814dff40>] sock_sendmsg+0xa0/0xc0
[  +0.000007]  [<ffffffff811566e9>] ? __do_fault+0x3c9/0x500
[  +0.000005]  [<ffffffff814e1930>] ? move_addr_to_kernel+0x40/0x90
[  +0.000005]  [<ffffffff814e18e3>] ___sys_sendmsg+0x373/0x380
[  +0.000006]  [<ffffffff8104eab4>] ? __do_page_fault+0x1d4/0x4d0
[  +0.000006]  [<ffffffff814e2382>] ? SyS_sendto+0x112/0x150
[  +0.000005]  [<ffffffff814e27c2>] __sys_sendmsg+0x42/0x80
[  +0.000005]  [<ffffffff814e2812>] SyS_sendmsg+0x12/0x20
[  +0.000006]  [<ffffffff815e7669>] system_call_fastpath+0x16/0x1b
[  +0.000003] ---[ end trace 9aea4b24782a1224 ]---
fixes-3.16: remove useless warning from tcp_fragment()

Not to screw dmesg of my numerous routers with this crap:

===
WARNING: CPU: 2 PID: 6144 at
/build/buildd/linux-3.11.0/net/ipv4/tcp_output.c:1073
tcp_fragment+0x2e6/0x2f0()
===

just remove WARN_ON() from if statement.

I guess this is related to tap or bridge configuration.
Merge branch 'fixes-3.16' into pf-3.16