mod-authtoken thread blocking on folio-snapshot-stable

Okapi on folio-snapshot-stable stopped responding 28 August. The Okapi log showed thread blocking on mod-authtoken. I've attached the log (unfortunately I destroyed the mod-authtoken container before retrieved mod-authtoken's own log, so I only have the Okapi log) – sorry, it's very long. We have not been able to duplicate the problem, filing this issue as a placeholder in case we come across it again.