Without this patch the guest pauses due to ENOMEDIUM. The guest is
stuck in a continuous pause loop since the I/O request is retried and
fails immediately again when the guest is resumed.
With this patch the error is reported to the guest.
Note that this scenario actually happens sometimes during libvirt disk
hot unplug, where device_del is followed by drive_del. I/O may still be
submitted to the drive after drive_del if the guest does not process the
PCI hot unplug notification.
Reported-by: Dafna Ron <dron@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com>