Update Linux firewall code to modern, supported distro versions
In hopes of helping @hibler solve Richard's need to firewall d710 machines behind a Linux firewall, I took a quick shot at simply running the firewall on Ubuntu 16. The generated firewall script bailed due to an unresolveable name
ntp1. Either there's a chicken and egg problem that the code never handled before, or there's a new problem. Either way, I will dig into this and hope for a simple solution that pulls forward Linux firewalls from Ubuntu 10.