osx: launch the firewall with admin privileges
if we want to support fail-close for vpn in this release, we need a solution for launching the firewall.
I have a working PoC:
server: https://gist.github.com/kalikaneko/e0819e41bc91c284c060 client: https://gist.github.com/kalikaneko/b9575cd9522d73091b00
(from redmine: created on 2015-10-08, relates #7521 (closed))