Updated check for systemd

Based on http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=703600
and http://cgit.freedesktop.org/systemd/systemd/commit/?id=66e411811b8090

This will probably need testing on a variety of oses.
Merge pull request #4647 from joehealy/systemd_check_changes

Updated check for systemd