vdev_destroy_unlink_zap
extern void vdev_destroy_unlink_zap(vdev_t *vd, uint64_t zapobj,
vdev_destroy_unlink_zap(vd, vd->vdev_leaf_zap, tx);
vdev_destroy_unlink_zap(vd, vd->vdev_top_zap, tx);
vdev_destroy_unlink_zap(vd, fnvpair_value_uint64(pair), tx);