MDL-25504 cron: Move delete unconfirmed users to task
MDL-25504 cron: Improve cron task mtrace format

Remove extra newlines.
MDL-25504 cron: Convert delete incomplete users to task
MDL-25504 cron: Convert delete old logs to task.
MDL-25504 cron: cleanup backup tables converted to task
MDL-25504 cron: Convert delete cache text to task
MDL-25504 cron: Convert tag cron to task
MDL-25504 cron: Convert context cleanup to task
MDL-25504 cron: Convert cache cleanup to task
MDL-25504 cron: convert messaging cleanup to task