[Libguestfs] [PATCH 0/6] v2v: Add drivers for virtio-rng, balloon, pvpanic.

Yaniv pointed out in https://bugzilla.redhat.com/show_bug.cgi?id=1438794 that virt-v2v both doesn't install the virtio-rng driver for Windows, and doesn't give the guest a virtio-rng PCI device either. There are two problems here: Firstly the Windows virtio-rng driver isn't included in the exploded tree (/usr/share/virtio-win) so it doesn't get copied into the guest. The solution is to prefer the virtio-win ISO over the exploded tree, since the ISO contains the complete set. We had support for reading the ISO for ages, so this just changes the default to search the ISO first (patch 6/6). Secondly we didn't model if the guest supports virtio-rng. If it does support it, we should add a virtio-rng device in the output metadata. Patch 1-5 add this modelling, and support for -o libvirt. I didn't (yet?) add support for -o rhv, because I couldn't see from the oVirt Engine source how to describe that in the OVF. As part of the same set of changes, I also added support for virtio-balloon and pvpanic, which work in basically the same way as virtio-rng, so it was convenient to add all three at the same time. Rich.