Using a Bitcoin-Qt v0.16.0 ([downloaded from bitcoin page](https://bitcoin.org/bin/bitcoin-core-0.16.0/bitcoin-0.16.0-osx.dmg)) in an macOS High Sierra 10.13.4 

When I start after a fresh install Bitcoin-Qt as a mainnet node and wallet, the wallet prompt that about 203gb is going to be used in my disk
![image](https://user-images.githubusercontent.com/20187136/39899688-ba820bfe-5493-11e8-87d9-460ed5716a02.png)

When I start the node and wallet as testnet, shows the same message about the 203gb disk usage
![image](https://user-images.githubusercontent.com/20187136/39899756-17b31214-5494-11e8-8a57-60e604e74afb.png)

It seems that the second time the message is wrong, due that the testnet database uses about 14gb.
{
    QString dir = QDir::toNativeSeparators(QFileDialog::getExistingDirectory(0, "Choose data directory", ui->dataDirectory->text()));
    if(!dir.isEmpty())
        ui->dataDirectory->setText(dir);
}
void Intro::on_dataDirDefault_clicked()
{
    setDataDirectory(getDefaultDataDirectory());
}
void Intro::on_dataDirCustom_clicked()
{
    ui->dataDirectory->setEnabled(true);
    ui->ellipsisButton->setEnabled(true);
}
void Intro::startThread()
{
    thread = new QThread(this);
    FreespaceChecker *executor = new FreespaceChecker(this);
    executor->moveToThread(thread);
    connect(executor, &FreespaceChecker::reply, this, &Intro::setStatus);
    connect(this, &Intro::requestCheck, executor, &FreespaceChecker::check);
    
    connect(this, &Intro::stopThread, executor, &QObject::deleteLater);
    connect(this, &Intro::stopThread, thread, &QThread::quit);
    thread->start();
}
void Intro::checkPath(const QString &dataDir)