Suppress QEMU default devices (CD, floppy)

[conath]

QEMU provides default devices for each virtual system. Due to the way the QEMU device "suppression" works, sometimes we end up with extra devices in the guest.

For example, when using a q35 guest with a USB CD drive added, the QEMU default IDE CD drive is still generated and visible in the guest, with no way to actually insert an ISO into it from UTM's UI.

In the above screenshot, you can see two CD drives. The top one is the QEMU default and the bottom one is the USB CD drive I added through the config/settings UI.

I'd suggest that the argument -nodefaults should be passed to all VMs, as UTM generates all the devices itself. I tested this with the VM from the above screenshot and it resolved the issue (the IDE CD drive disappeared from the guest and the USB one was still there).

-nodefaults suppresses all the default devices mentioned above, plus a few other things such as default SD-Card drive and default monitor.