QtIFW

Fix settings test

QFile either returns 'Unknown error' or 'No such file or directory'
when trying to use non-existing file. Make settings test
work with both values.

Change-Id: I5245b5ad0cf5b91a7eec61c17315982ce14eecfb
Reviewed-by: Iikka Eklund <iikka.eklund@qt.io>