We need to clean up vxlan despite vxlan_igmp_leave() fails.

This fixes the following kernel warning:

 WARNING: CPU: 0 PID: 6 at lib/debugobjects.c:263 debug_print_object+0x7c/0x8d()
 ODEBUG: free active (active state 0) object type: timer_list hint: vxlan_cleanup+0x0/0xd0
 CPU: 0 PID: 6 Comm: kworker/u8:0 Not tainted 4.0.0-rc7+ #953
 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
 Workqueue: netns cleanup_net
  0000000000000009 ffff88011955f948 ffffffff81a25f5a 00000000253f253e
  ffff88011955f998 ffff88011955f988 ffffffff8107608e 0000000000000000
  ffffffff814deba2 ffff8800d4e94000 ffffffff82254c30 ffffffff81fbe455
 Call Trace:
  [<ffffffff81a25f5a>] dump_stack+0x4c/0x65
  [<ffffffff8107608e>] warn_slowpath_common+0x9c/0xb6
  [<ffffffff814deba2>] ? debug_print_object+0x7c/0x8d
  [<ffffffff81076116>] warn_slowpath_fmt+0x46/0x48
  [<ffffffff814deba2>] debug_print_object+0x7c/0x8d
  [<ffffffff81666bf1>] ? vxlan_fdb_destroy+0x5b/0x5b
  [<ffffffff814dee02>] __debug_check_no_obj_freed+0xc3/0x15f
  [<ffffffff814df728>] debug_check_no_obj_freed+0x12/0x16
  [<ffffffff8117ae4e>] slab_free_hook+0x64/0x6c
  [<ffffffff8114deaa>] ? kvfree+0x31/0x33
  [<ffffffff8117dc66>] kfree+0x101/0x1ac
  [<ffffffff8114deaa>] kvfree+0x31/0x33
  [<ffffffff817d4137>] netdev_freemem+0x18/0x1a
  [<ffffffff817e8b52>] netdev_release+0x2e/0x32
  [<ffffffff815b4163>] device_release+0x5a/0x92
  [<ffffffff814bd4dd>] kobject_cleanup+0x49/0x5e
  [<ffffffff814bd3ff>] kobject_put+0x45/0x49
  [<ffffffff817d3fc1>] netdev_run_todo+0x26f/0x283
  [<ffffffff817d4873>] ? rollback_registered_many+0x20f/0x23b
  [<ffffffff817e0c80>] rtnl_unlock+0xe/0x10
  [<ffffffff817d4af0>] default_device_exit_batch+0x12a/0x139
  [<ffffffff810aadfa>] ? wait_woken+0x8f/0x8f
  [<ffffffff817c8e14>] ops_exit_list+0x2b/0x57
  [<ffffffff817c9b21>] cleanup_net+0x154/0x1e7
  [<ffffffff8108b05d>] process_one_work+0x255/0x4ad
  [<ffffffff8108af69>] ? process_one_work+0x161/0x4ad
  [<ffffffff8108b4b1>] worker_thread+0x1cd/0x2ab
  [<ffffffff8108b2e4>] ? process_scheduled_works+0x2f/0x2f
  [<ffffffff81090686>] kthread+0xd4/0xdc
  [<ffffffff8109eca3>] ? local_clock+0x19/0x22
  [<ffffffff810905b2>] ? __kthread_parkme+0x83/0x83
  [<ffffffff81a31c48>] ret_from_fork+0x58/0x90
  [<ffffffff810905b2>] ? __kthread_parkme+0x83/0x83

For the long-term, we should handle NETDEV_{UP,DOWN} event
from the lower device of a tunnel device.

Fixes: 56ef9c90 ("vxlan: Move socket initialization to within rtnl scope")
Cc: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>