Bugfix: util: Lower the threshold for considering pool Scrypt diff broken

I have a task out to add the #brokendiff and #nobrokendiff URIs. The current code in Git is broken for low diff Scrypt servers. The code prior to that is broken for Scrypt diffs (legit) greater than or equal to 1.

So I think this is a decent fix for what was broken, also works around broken P2Pool, and lets us push out a *more compatible* build before putting out one that breaks compatibility in favor of being truly *right*.