our export code can handle if the tape is inside the drive, so unloading
it first does not have an benefit, it even makes the exporting slower,
since we first unload it into its original slot, and then moving it
to an import/export slot
so drop the code that unloads the tape from the drive, and let the
export code itself handle that
change the 'eject' into a 'rewind' and comment why we do that first
Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>