Fix crash for pressing Ctrl+C in a message box

This fixes a regression introduced with e34dccc9e

Task-number: QTBUG-31635
Change-Id: I7c991f3b98f5c51e5fb3c12db04d3ace7be87010
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Mitch Curtis <mitch.curtis@digia.com>
Let QTemporaryDir::stressTest() run in temporary directory.

Task-number: QTBUG-31618

Change-Id: I60aaa4f57710816cd0e22ea9b097c7e85466fd0c
Reviewed-by: David Faure (KDE) <faure@kde.org>