Fix EZP-23687: Notice when running "$phpbin runcronjobs.php monitor"

array_diff() does not work recursively. Compare serialize() output instead, since we just want to check if the arrays are equal.
Merge pull request #1117 from glye/ezp-23687_notice_when_running_monitor_cronjob

Fix EZP-23687: Notice when running "$phpbin runcronjobs.php monitor"