Make authority_control_fields.pl resistant to database timeouts

Make authority_control_fields.pl resistant to database timeouts

LP 771237 describes how on an underpowered system, the work that
authority_control_fields.pl tries to do on a per-record basis may hit the
CStore default timeout of 6 seconds for a transaction and automatically
end the transaction, resulting in no work being committed once the script tries
to update the bibliographic record. Searching each controlled field for a
matching authority record can be costly in a database with millions of
authority records.

To enable the script to accomplish its work on underpowered test systems, use a
regular read-only CStoreEditor session to accomplish the lookups and create a
separate CStoreEditor session to issue the update in a transaction if required.

Signed-off-by: Dan Scott <dscott@laurentian.ca>
git-svn-id: svn://svn.open-ils.org/ILS/branches/rel_2_1@20312 dcc99617-32d9-48b4-a31d-7c20da2025e4