score: fix __get_user/get_user

commit c2f18fa4cbb3ad92e033a24efa27583978ce9600 upstream.

* should zero on any failure
* __get_user() should use __copy_from_user(), not copy_from_user()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Willy Tarreau <w@1wt.eu>