function rollbackSave(db, save, task) {
  var collection = getCollectionForStep(db, save);
  var _id = save.dataStore[0]._id;

  return collection.deleteOne({_id: _id}).then(function(){
    return updateState(task, save.index, ROLLED);
  });
}
Rollback for a save step

@param db native db
@param save the save step
@param task the task containing the step

@returns {Promise|*}