virtio-blk: Add blk_drain() to virtio_blk_device_unrealize()

QEMU does not wait for completed I/O requests, assuming that the guest
driver will reset the device before calling unrealize(). This does not
happen on Windows, and QEMU crashes in virtio_notify(), getting the
result of a completed I/O request on hot-unplugged device.

Signed-off-by: Julia Suvorova <jusual@redhat.com>
Message-Id: <20191018142856.31870-1-jusual@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
1 file changed