pe_get_device_dos_drive_letter(): open the drive, not the volume.
    
    Opening the drive rather than the volume's top-level directory requires
    reduced permissions, and so should always be preferred for as long as
    it is sufficient.
    
    This change, however, is also motivated by annoying media-drive driver
    behavior of popping up a dialog (how awful) window whenever an allegedly
    interactive application (that is, interactive by its subsystem) attempts
    to access a directory (or a file) in the drive while it is empty.