Adding an attack-box for VPN-events

[olnor18]

Along with the normal challenges, it would be nice to have an "attack-box", which could just be a linux machine with some tools like tcpdump and similar, allowing VPN-events to work with challenges that require proper network access to the challenge-network. An example could be the wireshark challenges. This would also be needed in some typical relay-attacks from the AD world if those ever make their way onto Hauukins