Opening an optical drive device node without O_NONBLOCK autocloses the
tray, we run vol_id on every media change by kernel emitted "change"
events, which can make it hard to change the media when the tray closes
immediatey again.:) We check for cdrom_id to indicate an existing track,
if no media is found, we will not open the device with vol_id.
Thanks to Christian Krause and DavidZ for debugging and testing.
Kay Sievers
f755fd5657