[Libguestfs] [PATCH virt-v2v] v2v: windows: Install both legacy and modern virtio

Hello Roman, We have a bug with Windows 8 UEFI conversions failing with the usual 0x7B error: https://bugzilla.redhat.com/show_bug.cgi?id=1431579 There is a seemingly plausible theory that this happens because for UEFI we use a qemu Q35 machine type. Q35 machine type implies all-modern PCI-e devices, which implies the use of virtio-1.0 and disabling of virtio legacy. Virtio-1.0 uses different Windows registry keys: viostor changes from VEN_1AF4&DEV_1001&SUBSYS_00021AF4&REV_00 -> VEN_1AF4&DEV_1042&SUBSYS_11001AF4&REV_01, and vioscsi has a similar change. As we are only installing the virtio legacy key, but presenting PCI-e virtio-1.0 (modern) devices to the guest, this may cause Windows to fail to boot. I have not gone beyond compile-testing the attached patch, but what do you think? I will try to actually test this tomorrow, but I wondered if you have any comments. Thanks, Rich.