FactPlugin does not set a notification task end property

Current Situation

• In some cases, if an order task ends much later than the order / step then the value of the variable SCHEDULER_MON_NOTIFICATIONS.TASK_END_TIME will be empty and will not be updated when the task completes.
• This behaviour can occur if an idle_timeout is configured for a job.

Desired behaviour

• The FactPlugin should update all notification properties correctly.