Set START=yes when runmode=="service"

This fork is for debian based system. In this system, agent run is control with variable START from /etc/default/puppet. Since this option is by default set to "no", even when you use runmode == 'service' in your manifest, puppet agent is not run.
In this fork I have added code to set that variable to "yes" when runmode is set to "service" and the system is debian based.