class Rufus::Scheduler

Currently used only in unit tests.

there aren't no more 'at' (or 'every') jobs in the scheduler.
Thus the scheduler will exit (and the join terminates) as soon as
attribute of this scheduler to true before joining.
Like join() but takes care of setting the 'exit_when_no_more_jobs'

def join_until_no_more_jobs
  @exit_when_no_more_jobs = true
  join
end