nixos-module/container/anon: make nat, iproute2 config optional

nix/nixos-module/container/anon.nix

@@ -98,7 +98,7 @@ in
     '';
   }) tunnels;
 
-  networking.nat = lib.optionalAttrs enabled {
+  networking.nat = lib.mkIf enabled {
     enable = true;
     enableIPv6 = true;
     internalInterfaces = [ "core" ];
@@ -107,7 +107,7 @@ in
   };
 
   # Configure rt_table name
-  networking.iproute2 = {
+  networking.iproute2 = lib.mkIf enabled {
     enable = true;
     rttablesExtraConfig = ''
       ${toString vpn4Table} vpn4