[pve-devel] qemu-server : iothread and multiqueues implementation

[Alexandre Derumier]

This rework iothread implementation,

add support for iothread for virtio-blk and virtio-scsi
also add virtio-scsi multiqueue support.

(for virtio-scsi, iothread and queues are only supported by controller,
 so I have make some change to enable 1controller by virtio-scsi disk if iothread or queues are enabled).

I have tried to keep commits are small as possible for review