nixops: open port 6000 on rpi2

nixops/rpi.nix

@@ -43,6 +43,9 @@ in
   programs.mosh.enable = true;
 
   networking.hostName = host;
+
+  networking.firewall.allowedTCPPorts = if host == "rpi-2" then [ 6000 ] else [];
+
   time.timeZone = "Asia/Hong_Kong";
 
   users.extraGroups.plugdev = { };