Btrfs: properly clean up btrfs_end_io_wq_cache
Btrfs: properly clean up btrfs_end_io_wq_cache

In one of Dave's cleanup commits he forgot to call btrfs_end_io_wq_exit on
unload, which makes us unable to unload and then re-load the btrfs module.  This
fixes the problem.  Thanks,

Signed-off-by: Josef Bacik <631dfb3d07694fdcf26abc7aac2c6c2b641f8bde@fb.com>
Reviewed-by: David Sterba <a2ce9d316ca04d17b520237d2846a218b8284e52@suse.cz>
Reviewed-by: Miao Xie <d7fac3f7b328449401fe64671e732ac315caee28@cn.fujitsu.com>
Signed-off-by: Chris Mason <e2e8c5702d8ed5f565988a1cf5bb35c9ce199e5e@fb.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs