CDROM still does not work in 2.4.0-test6

[Eugene Crosser]

This apparently happened in test5 and is the same in test6.
When you umount cdrom, put another one and mount it, you
still see directory from the first cdrom.  When you try to
read files, you get errors.

When you umount a cdrom, try to mount empty drive (which fails),
then put in a new cdrom and mount it, you now can see directory
of the new cdrom and can read the files.

Cdrom is SCSI Plextor on ncr53c810 controller, SMP kernel on
dual Pentium MMX board.

Eugene