NetKVM: BZ#950611 Guest offloads configuration via control queue

This is a part BZ#950611 implementation.
RSC should be configurable in run-time without driver reload.
Bug 889941 - [virtio-win][scsi] virtio_scsi driver performs bad during large buffers transfer
NetKVM: BZ#950611 Guest offloads configuration via control queue

Broken pre-Win8 compilation fixed