haas-proxy: refactor init script
This changes how cgroups are set for haas-proxy. It also tweaks firewall and more.
Resolves: https://gitlab.labs.nic.cz/turris/turris-os-packages/issues/367 and https://gitlab.labs.nic.cz/turris/turris-os-packages/issues/394
Edited by Josef Schlehofer