Problems with QXmlStreamWriter related GUI unit tests

• TestJobRealModel often fails, with timeout from Tests/Unit/GUI/TestJobRealModel.cpp line 98 (current work around: wait 300ms after each write)
• test log contains numerous lines "QXmlStreamWriter: No device" => no longer the case
• Unit.GUI.TestAutosaveController.autosaveEnabled takes 10 sec #522 (closed) => test accelerated since long, and removed for other reason
• why do some tests need QTest::qSleep? => one single test, not a concern