ZFS_UNLINKED_SET
error = zap_lookup(os, MASTER_NODE_OBJ, ZFS_UNLINKED_SET, 8, 1,
error = zap_add(os, moid, ZFS_UNLINKED_SET, 8, 1, &obj, tx);
ZFS_UNLINKED_SET, sizeof (uint64_t), 1, &deleteq_obj));