Fix for update-rc.d based systems that also have systemd installed

By default, the service module had assumed that if the system had the
update-rc.d binary, the service was either managed via upstart or standard
sysV init-style scripts. This patch adds a check for systemctl ahead
of the other methods when update-rc.d is detected, and also simplifies
the logic around the detection of systemctl-managed services
Minor fix to account for template service names in systemctl