tstQFile_moveToTrash may try to wipe the device

The tstQFile_moveToTrash test can attempt to wipe the entire device when the device is nearly full.  In this situation, the QTemporaryDir variables created by the data function may be invalid because the temporary directory can't be created.  This causes the data function to attach "/" to nothing for the "temporary dir" and/or "home dir" tests.  The tests proceed to wipe as much of the device as they can before they run out of time.  I was oh so glad that this was running on a device that didn't have anything important on it and was easily re-imaged.