As @bobvanderlinden suggests in #13585:
"Looks like that cleans things up quite a bit! Just one aesthetics note,
the boot tests could now be renamed from boot.bootBiosCdrom to
boot.biosCdrom in nixos/tests/boot.nix:L33.
That makes them more consistent with the other tests."
Signed-off-by: aszlig <aszlig@redmoonstudios.org>