QSettings::sync() causes "QWarning setNativeLocks failed"

When QSettings::setValue() or QSetting::sync() is called, a qWarning may be emitted:

setNativeLocks failed: Resource temporarily unavailable

Despite the warning, settings seem to write/read correctly. This does not occur on all linux platforms I've tested. This warning only appeared after porting from Qt4.8 to Qt5.4.1

My speculation is that this warning is emitted only when the settings .conf file is located on a network mounted drive. I think this because all the machines that exhibit this warning that I've tested use a network mounted drive for the home directory. I've tested this on virtual machines that I've created with local drives and they do not exhibit the problem.

I've attached a "minimal" example that exhibits the issue. However, any application that writes settings seems to emit the warning:

1. extract
2. qmake
3. make
4. ./qsettingstest
5. Press the Write Settings button
6. See QWarning in terminal