Avoid collisions of normalized values going into metabib.browse_entry

Avoid collisions of normalized values going into metabib.browse_entry

This fixes a bug that prevents successful reingestion of bib records in
some cases.  Reported by George Duimovich.  Key part here:

> ERROR: duplicate key value violates unique constraint
> "browse_entry_value_key"
> DETAIL: Key (value)=(545575) already exists.
> CONTEXT: SQL statement "INSERT INTO metabib.browse_entry (value) VALUES
>                     (metabib.browse_normalize(ind_data.value,

Signed-off-by: Lebbeous Fogle-Weekley <lebbeous@esilibrary.com>