nixos-build-vms(8): `$out/bin/nixos-run-vms` should non-interactively start VMs

Not entirely sure when it got broken this time, but when creating a VM
network with `nixos-build-vms(8)`, there are should be the following scripts:

* `$out/bin/nixos-test-driver` which drops into an interactive shell to
  interactively perform test steps.
* `$out/bin/nixos-run-vms` which non-interactively starts the VMs from
  the network so that one can manually play around in the VM.

The latter also starts an interactive shell for a while now which means
that it does the exact same thing as `nixos-test-driver` which is not
its purpose.

nixos/modules/installer/tools/nixos-build-vms/build-vms.nix

@@ -25,4 +25,7 @@ pkgs.runCommand "nixos-build-vms" { nativeBuildInputs = [ pkgs.makeWrapper ]; }
   ln -s ${interactiveDriver}/bin/nixos-test-driver $out/bin/nixos-run-vms
   wrapProgram $out/bin/nixos-test-driver \
     --add-flags "--interactive"
+  wrapProgram $out/bin/nixos-run-vms \
+     --set testScript "${pkgs.writeText "start-all" "start_all(); join_all();"}" \
+     --add-flags "--no-interactive"
 ''