MFC of "Large set of CAM improvements" breaks I/O to Adaptec 29160 SCSI controller

[Pete French]

> Seems like I've found the reason. Attached patch fixes problem for me.

Inetersting - one of my machines has ginished a gmirror resync. The first
time I tried this it did lock up, but with media rea errors (which may be
genuine on these old drives). But this tiime it has finished, and without
the patch this machine would never finish a rebuild.

So far, so good...

-pete.