This enables the virtio-scsi-dataplane code by setting the iothread
in virtio-scsi device, and makes any function that is called by
back from dataplane to cooperate with the caller: they need to be
vring/iothread aware when handling the requests and using scsi devices
on the bus.
Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>