Race condition in the remote size loading logic

The quota retrieval process might not be finished by the time
the used space on the server (`_rSize`) is compared against
the locally available disk space which might end up in
a "There isn't enough free space in the local folder!" message
even if there is enough free space.

This patch updates the status after the quota has been retrieved.

It also initializes `_rSize` to `-1` so that errors like this
are easier to catch in the future.

src/gui/wizard/owncloudadvancedsetuppage.cpp

@@ -42,6 +42,8 @@ OwncloudAdvancedSetupPage::OwncloudAdvancedSetupPage()
     , _localFolderValid(false)
     , _progressIndi(new QProgressIndicator(this))
     , _remoteFolder()
+    , _rSize(-1)
+    , _rSelectedSize(-1)
 {
     _ui.setupUi(this);
 
@@ -368,6 +370,8 @@ void OwncloudAdvancedSetupPage::slotQuotaRetrieved(const QVariantMap &result)
 {
     _rSize = result["size"].toDouble();
     _ui.lSyncEverythingSizeLabel->setText(tr("(%1)").arg(Utility::octetsToString(_rSize)));
+
+    updateStatus();
 }
 
 qint64 OwncloudAdvancedSetupPage::availableLocalSpace() const