btrfs: do not decrease bytes_may_use when replaying extents

When replaying extents, there is no need to update bytes_may_use
in btrfs_alloc_logged_file_extent(), otherwise it'll trigger a
WARN_ON about bytes_may_use.

Fixes: ("btrfs: update btrfs_space_info's bytes_may_use timely")
Signed-off-by: Wang Xiaoguang <wangxg.fnst@cn.fujitsu.com>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>