nixos: Make nesting.children work in NixOS tests

We differentiate between modules and baseModules in  the
VM builder for NixOS tests. This way, nesting.children, eventhough
it doesn't inherit from parent, still has enough config to
actually complete the test. Otherwise, the qemu modules
would not be loaded, for example, and a nesting.children
statement would not evaluate.

nixos/lib/build-vms.nix

@@ -32,14 +32,14 @@ rec {
 
     import ./eval-config.nix {
       inherit system;
-      modules = configurations ++
+      modules = configurations ++ extraConfigurations;
+      baseModules =  (import ../modules/module-list.nix) ++
         [ ../modules/virtualisation/qemu-vm.nix
           ../modules/testing/test-instrumentation.nix # !!! should only get added for automated test runs
           { key = "no-manual"; documentation.nixos.enable = false; }
           { key = "qemu"; system.build.qemu = qemu; }
           { key = "nodes"; _module.args.nodes = nodes; }
-        ] ++ optional minimal ../modules/testing/minimal-kernel.nix
-          ++ extraConfigurations;
+        ] ++ optional minimal ../modules/testing/minimal-kernel.nix;
     };