f2fs: fix a bug of inheriting default ACL from parent

Introduced by a6dda0e6
"f2fs: use generic posix ACL infrastructure".

When testing default acl, gets in recent kernel (3.19.0-rc5),
user::rwx
group::r-x
other::r-x
default:user::rwx
default:group::r-x
default:group:root:rwx
default:mask::rwx
default:other::r-x

]# getfacl testdir/
user::rwx
group::rwx
                // missing an acl "group:root:rwx" inherited from parent
other::r-x
default:user::rwx
default:group::r-x
default:group:root:rwx
default:mask::rwx
default:other::r-x

Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
Reviewed-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>