auto-rollback install instance count wrong

[James Olin Oden <joden malachi lee k12 nc us>]

Hi Jeff,

I just found a bug in my auto-rollback patch.  Appearantly,
whenever I run the rollback transaction, and an install
scriptlet for a package being upgraded is ran, its instances 
is 3.  I actually understand why this happening.  For instances
if events transpire as so:

	p1 installed.
	p2 fails.

Then at that point there are still two headers in db for p1 (provided
it was being upgraded.  The problem is this will not always be the
case, for instance:

	p1 installed.
	p2 installed.
	p1 erased (old pkg).
	p2 erase fails (old pkg).

Then in this case the actual instances in the db would be 1 as 
the erase of the old pkg header has occured.  

If it was always off, I could figure out a fix quick (even something ugly 
like creating a global in the psm called autorollback, and doing
the right thing based on it being true or false), but since the right
thing depends on how far along things got I am not sure how to tackle 
this?

Any clues?

Thanks...james