virtio-blk: allow drive_del with dataplane

Now that drive_del acquires the AioContext we can safely allow deleting
the drive.  As with non-dataplane mode, all I/Os submitted by the guest
after drive_del will return EIO.

This patch makes hot unplug work with virtio-blk dataplane.  Previously
drive_del reported an error because the device was busy.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

hw/block/dataplane/virtio-blk.c

@@ -194,6 +194,7 @@ void virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *blk,
     error_setg(&s->blocker, "block device is in use by data plane");
     bdrv_op_block_all(blk->conf.bs, s->blocker);
     bdrv_op_unblock(blk->conf.bs, BLOCK_OP_TYPE_RESIZE, s->blocker);
+    bdrv_op_unblock(blk->conf.bs, BLOCK_OP_TYPE_DRIVE_DEL, s->blocker);
 
     *dataplane = s;
 }