Breaks hotplug:
Running tests/device-add.sh
Using RANDOM seed 24922
Formatting '.tmp-28149/disk.img', fmt=qcow2 size=10737418240 encryption=off
cluster_size=65536 lazy_refcounts=off
/home/aliguori/build/qemu/x86_64-softmmu/qemu-system-x86_64 -kernel
/usr/local/share/qemu-jeos/kernel-x86_64-pc
From: KONRAD Frederic
This is the next part of virtio-refactoring.
Basically it creates virtio-blk device which extends virtio-device.
Then a virtio-blk can be connected on a virtio-bus.
virtio-blk-pci, virtio-blk-s390x, virtio-blk-ccw are created too, they extend
respectively virtio-pci, virtio
