Remove extra flush commands on firewall stop

They are not needed as they are already flushed when the firewall
starts or stops.

m/apex/nfs.nix

@@ -28,10 +28,5 @@
       iptables -A nixos-fw -p udp -s 10.0.40.0/24 --dport 4002  -j nixos-fw-accept
       iptables -A nixos-fw -p udp -s 10.0.40.0/24 --dport 20048 -j nixos-fw-accept
     '';
-    # Flush all rules and chains on stop so it won't break on start
-    extraStopCommands = ''
-      iptables -F
-      iptables -X
-    '';
   };
 }

m/common/base/net.nix

@@ -1,4 +1,4 @@
-{ pkgs, ... }:
+{ pkgs, lib, ... }:
 
 {
   networking = {
@@ -10,6 +10,9 @@
       allowedTCPPorts = [ 22 ];
     };
 
+    # Make sure we use iptables
+    nftables.enable = lib.mkForce false;
+
     hosts = {
       "84.88.53.236" = [ "apex" "ssfhead.bsc.es" "ssfhead" ];
       "84.88.51.152" = [ "raccoon" ];