Missed operation lists always run when the scheduler is reenabled

See PUBEB-75. If an operation list is due to run while the scheduler is disabled, the operation list will run as soon as the scheduler is reenabled, eg. once a week every Saturday night, scheduler disabled, the operation list runs on Monday when the schedule is reenabled.

This is because stopping the scheduler only stops the Timer in the PollingScheduleDecorator. The jobs are polled on the event that the timer is incremented, so this prevents the operation lists from running. However, the NextRun information of timings is not updated, and as such the timings say they are due to run.

The most ideal fix here would be to force timings to run CalculateNextRunAfterTime when the schedule is reenabled to recalculate their next run information. For operation lists marked as QueueMissed, these will need to be added to the queue and executed when the scheduler is reenabled. Although the changes may be minor, they have potentially far reaching effects, and all scheduling options should be thoroughly regression tested following the changes.

This issue will also affect Identity Broker 4.