Author: Alexey Sokolov <alexey@...>
Date: 2012-10-28 (Sun, 28 Oct 2012)
Fix installing without root when systemd exists.
Try to detect path to systemd units only when
--with-systemdsystemunitdir is used without the path.
If this option isn't specified at all, no need to install systemd file.
Thanks to n0kS for reporting this.