Fix stacked runlevel support

Patch was provided by  Max Hacking <max.gentoo.bugzilla@hacking.co.uk>
and slightly fixed by Alexander Vershilov <qnikst@gentoo.org>

X-Gentoo-Bug: #467368
X-Gentoo-Bug-Url: https://bugs.gentoo.org/show_bug.cgi?id=467368