coordinator not available error should cause add into unmap list to do a new lookup

case COORDINATOR_LOAD_IN_PROGRESS:
    // If the coordinator is in the middle of loading, then we just need to retry
    log.debug("DescribeTransactions request for transactionalId `{}` failed because the " +
            "coordinator is still in the process of loading state. Will retry",
        transactionalIdKey.idValue);
    break;

case NOT_COORDINATOR:
case COORDINATOR_NOT_AVAILABLE:
    // If the coordinator is unavailable or there was a coordinator change, then we unmap
    // the key so that we retry the `FindCoordinator` request
    unmapped.add(transactionalIdKey);
    log.debug("DescribeTransactions request for transactionalId `{}` returned error {}. Will attempt " +
            "to find the coordinator again and retry", transactionalIdKey.idValue, error);
    break;