rc-status: fix infinite  loop when using stacked runlevels

Remove the recursive call in print_stacked_services which was causing an
infinite loop when using stacked runlevels.
I would like to thank Doug Freed and Jason Zaman for assisting with
tracking this down.

X-Gentoo-Bug: 514972
X-Gentoo-Bug-URL: https://bugs.gentoo.org/show_bug.cgi?id=514972