Re-enable collaborative mode doesn't remove all stale drafts

Issue Summary

Turning collaborative editing mode off and on again triggers a stale drafts auto cleanup but sometimes, there are stale drafts were not deleted successfully. 

Steps to Reproduce

1. turn collaborative mode off and on
2. run query 

SELECT d.contentid, d.title, d.prevver, d.lastmoddate, c.lastmoddate
FROM CONTENT d
JOIN CONTENT c
  ON d.prevver = c.contentid
WHERE d.content_status = 'draft'
  AND d.prevver IS NOT NULL
  AND c.lastmoddate >= d.lastmoddate;

Expected Results

All stale draft pages should be deleted

Actual Results

There are old stale drafts remained in db

Workaround

https://confluence.atlassian.com/confkb/how-to-manually-remove-stale-drafts-from-confluence-database-951392345.html