btrfs_limit_group use arg limit to override the old qgroup_limit of
corresponding qgroup. However, we should override part of old qgroup_limit
according to the bit which has been set in arg limit.
Signed-off-by: NFan Chengniang <fancn.fnst@cn.fujitsu.com>
Signed-off-by: NDongsheng Yang <yangds.fnst@cn.fujitsu.com>
Signed-off-by: NChris Mason <clm@fb.com>