nixos: Fix iso_graphical evaluation

I broke it:
in job ‘nixos.iso_graphical.x86_64-linux’:
The option `services.udisks2.enable' has conflicting definitions, in `/nix/store/bwcjw1ddj94q83vbbnq1nnrs5aisaw59-source/nixos/modules/profiles/installation-device.nix' and `/nix/store/bwcjw1ddj94q83vbbnq1nnrs5aisaw59-source/nixos/modules/services/x11/desktop-managers/plasma5.nix'.

Changed files
+2 -2
nixos
modules
+2 -2
nixos/modules/profiles/installation-device.nix
···
#services.rogue.enable = true;
# Disable some other stuff we don't need.
-
security.sudo.enable = false;
-
services.udisks2.enable = false;
+
security.sudo.enable = mkDefault false;
+
services.udisks2.enable = mkDefault false;
# Automatically log in at the virtual consoles.
services.mingetty.autologinUser = "root";