fix rc_service_extra_commands return value
fix rc_service_extra_commands return value

If there were no extra commands, rc_service_extra_commands returned a
list containing a single empty string. This changes that to return an
empty list, which is more consistent with what you would expect.

X-Gentoo-Bug: 360013
X-Gentoo-Bug-URL: http://bugs.gentoo.org/show_bug.cgi?id=360013

OpenRC/openrc,OpenRC/openrc,williamh/openrc,dwfreed/openrc,dwfreed/openrc,OpenRC/openrc,williamh/openrc,dwfreed/openrc,williamh/openrc