tests/vhost-user-bridge: implement logging of dirty pages During migration devices continue writing to the guest's memory. The writes has to be reported to QEMU. This change implements minimal support in vhost-user-bridge required for successful migration of a guest with virtio-net device. Signed-off-by: Victor Kaplansky <victork@redhat.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>