[FEATURE] Scheduler task should synchronize backend users

Resolves: #60966
Change-Id: I43b0790d30a9bb103f27cdab93bbc2957f96e1a0
Reviewed-on: http://review.typo3.org/32153
Reviewed-by: Xavier Perseguers <xavier@typo3.org>
Tested-by: Xavier Perseguers <xavier@typo3.org>