Add firewall rules for Ceph and monitoring

The firewall was blocking the monitoring traffic from hut and the Ceph
traffic among OSDs. The rules only allow connecting from the specific
host that they are supposed to be coming from.

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

m/lake2/configuration.nix

@@ -45,6 +45,14 @@
       address = "10.0.42.42";
       prefixLength = 24;
     } ];
+    firewall = {
+      extraCommands = ''
+        # Accept all incoming TCP traffic from bay
+        iptables -A nixos-fw -p tcp -s bay -j nixos-fw-accept
+        # Accept monitoring requests from hut
+        iptables -A nixos-fw -p tcp -s hut --dport 9002 -j nixos-fw-accept
+      '';
+    };
   };
 
   # Missing service for volumes, see: