Better handling of TEST UNIT READY command

[Rafal Jaworowski]

Hi Scott,
Can you have a look at this patch:
http://people.freebsd.org/~raj/patches/misc/sys-cam-cam_xpt.diff

Greg was trying to discuss this on scsi@ already, but there wasn't much
response, so your input would be appreciated.

The description of the problem and fix is included in the patch, but if you'd
have any questions let me know.

Rafal