command on drives that don't like it. Right now, there's just a bogus
quirk entry in the table that doesn't do anything, but that should be
changed once we get actual inquiry data for drives that don't like the
synchronize cache command.
Also, add a shutdown hook that runs through all direct access peripherals
and runs a synchronize cache on them if they're still open, and if
synchronize cache isn't disabled via a quirk entry.
Add a synchronize cache call at the end of dadump() (again, conditionalized
on the quirk entry), so we can insure that the disk cache contents get
flushed to physical media after a dump.
Check the new quirk entry in daclose() to decide whether or not to
synchronize the cache for a disk at final close.
Reviewed by: gibbs
68c2a3a49f