foris-controller-openvpn_client-module: fix forwarding from guest to vpn client
requested to merge hotfix/foris-controller-openvpn_client-module-fix-guest-net-forwarding into master
There was missing firewall forward rule between "guest_turris" and "tr_vpn_cl" zones.
Adding this forwarding fixes "guest" network internet connectivity issue, when traffic from "guest" network is routed through VPN.
I.e.: You should be able to get to the internet when connected to guest network.
Closes: #805