Make apex host specific to each machine

Allows direct contact via the VPN when accessing from fox, but use
Internet when using the rest of the machines.

Reviewed-by: Aleix Roca Nonell <aleix.rocanonell@bsc.es>

m/raccoon/configuration.nix

@@ -39,6 +39,7 @@
     };
     hosts = {
       "10.0.44.4" = [ "tent" ];
+      "84.88.53.236" = [ "apex" ];
     };
   };