We cannot evict mixed mode tombstone when checkpoint is running

    onpage_upd = upd_select->upd != NULL && upd_select->upd->type == WT_UPDATE_TOMBSTONE ?

      NULL :

      upd_select->upd;

    /* Check the update chain for conditions that could prevent it's eviction. */

    WT_RET(__rec_validate_upd_chain(session, r, onpage_upd, select_tw, vpack));