Fix broken ISBN cleaning, handle missing keys

Fix broken ISBN cleaning, handle missing keys

Previous attempt at ISBN cleaning was broken. This approach
is not broken.

If we find no valid ISBN and no UPC values in the record,
do not attempt to call an AC handler. This will need
to change when we have AC handlers that rely on other
possible keys.

Caching improvement: serve from cache before fetching keys
from the bib record in the database.

Also:
* Fixed a stray "next" left over from an earlier re-factor.
* Removed some debugging.

Signed-off-by: Jeff Godin <jgodin@tadl.org>