Revert "virtualization/qemu-vm: fix and improve virtio/scsi switching"

This reverts commit f777d2b7.
cc #34409
This breaks evaluation of the tested job:
attribute 'diskInterface' missing, at /nix/store/5k9kk52bv6zsvsyyvpxhm8xmwyn2yjvx-source/pkgs/build-support/vm/default.nix:316:24