[Interest] QSettings stale lock file

[Michael Sué]

And there is also this bug QTBUG-43454 which in fact makes QSetting unusable in our Linux setup due to QLockFile since Qt 5.4.0.
- Michael.

>    * [QTBUG-21739] The locking mechanism inside QSettings has changed
>      and is no longer compatible with the one of previous versions of
>      Qt. There might be corruption if two applications running different
>      versions of Qt are writing to the same config file at the same
>      time. You must also now have write permissions in the directory
>      containing the settings file in order to write settings.