host: opt: network: Added workaround for systemd-networkd-wait-online…

….service timing out on generation activation

This is caused by nmcli waiting on the mullvad wiregaurd network device to be up,
which never happens. The workaround is adding the device, wg0-mullvad, to the unmanaged devices list.
Upstream issue is NixOS/nixpkgs#180175 .

host/opt/network.nix

@@ -38,7 +38,10 @@ in {
     };
 
     networking = {
-      networkmanager.enable = lib.mkDefault true;
+      networkmanager = {
+        enable = lib.mkDefault true;
+        unmanaged = lib.mkIf config.services.mullvad-vpn.enable ["wg0-mullvad"];
+      };
       firewall = {
         enable = true;
         checkReversePath = lib.mkDefault false;