ovl: copyattr after setting POSIX ACL

Setting POSIX acl may also modify the file mode, so need to copy that up to
the overlay inode.

Reported-by: Eryu Guan <eguan@redhat.com>
Fixes: d837a49b ("ovl: fix POSIX ACL setting")
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>