Looping by mistake over all jobs array (instead of all actual jobs)

[prassag]

func Scheduled(j interface{}) bool will crash when the answer if false
The function loops over all defaultScheduler.jobs which may (and probably will be) at least partially nil (if not all MAXJOBNUM are used).
Every loop over this array must be using the index and run up to size.

This is true also for func (s *Scheduler) Scheduled(j interface{}) bool