nixos/libvirtd: Take ethertypes from iptables-nftables-compat
nixos/libvirtd: Take ethertypes from iptables-nftables-compat

iptables is currently defined in `all-packages.nix` to be
iptables-compat. That package does however not contain `ethertypes`.
Only `iptables-nftables-compat` contains this file so the symlink
dangles.

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs