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

[Pete French]

> RELENG_8 csup'd with date=2010.02.14.00.00 works perfectly for days.
>
> RELENG_8 csup'd with date=2010.02.15.00.00 dead-locks the disk I/O
> subsystem. Network still operational but anything needing disk hangs.
> Power-cycle required.

An aditional point (and thanks to Andy for doing all the work to
identify the changes which cause the problems) this appears to be
the cause of the problem I have with gmirror since upgrading. I only
see this on SCSI systems too, and both my systems are using Adaptec
controllers, as is Andy's system.

-pete.