Fix audit purge script to remove entries without extended info

https://doc.nuxeo.com/nxdoc/purging-audit-logs-nxp_logs/ describes the way to purge the SQL audit logs.

The audit entries that have no extended info are not removed by theses procedures, so lots of entries remain unduly.

In adding the following to the SQL script:

DELETE FROM nxp_logs
    WHERE nxp_logs.log_event_date < maxDate::date
  GET DIAGNOSTICS nblines = ROW_COUNT;
  SELECT nblines+total INTO total;
  RAISE INFO '% lines cleanup on table nxp_logs', nblines;

you can get rid on the undue entries.