Cleanup network interfaces

[evgeniy-scherbina]

If boundary completes with an error or boundary process is killed, it doesn't make proper cleanup, and then user has to manually run:

ip link show
ip -o link show | awk -F': ' '{print $2}' | grep '^veth_h' | cut -d'@' -f1 | xargs -r -n1 sudo ip link delete

We should make sure clean up is always executed (network interfaces are removed, iptables rules are removed).
Consider running cleanup on startup? Consider adding cleanup command.