[9front] nusb/disk: lun 1 is not a disk (type 0xd)

[9front] nusb/disk: lun 1 is not a disk (type 0xd)

[unobe]

I purchased a WD Elements 5GB drive a while ago, and laid it aside
because when I plugged it in, I got:

	nusb/disk: lun 1 is not a disk (type 0xd)

And it failed to show in /dev.  I plugged it in to an old Macbook and
found that it was recognized with three partitions, two appearing to
be equally sized and the last being "grayed out"/unreadable.  I had to
re-partition w/MBR for it to then be recognized by 9front.  I
initially had plans work on it at the time because I didn't think that
one lun not being a disk should fail making the drive visible, but
that is indeed what /sys/src/cmd/nusb/disk/disk.c:374 does.  0xd, from
what I gather from the SCSI interface manual[1] on page 96, table 61,
the peripheral device type is being recognized as an encluse services
device.

Since I already formatted the drive, I'd have to buy another one to
investigate further, but thought I'd write this for posterity in case
anyone else comes across the same sort of thing.

[1] https://www.seagate.com/files/staticfiles/support/docs/manual/Interface%20manuals/100293068j.pdf . The link is flaky, returning 503 often.  I have a local copy.