actor statusLoop are not stopped correctly

As for now, an infinite number of status loop can be created.

running = self.monitors[controller] > 0
if (not running) and period > 0:
    self.statusLoopCB(controller)

If the monitoring period is set to 0 and then set back to a value before the statusLoop is called, two loops stay alive.

One solution would be to cancel the job if the monitoring period is set to 0 
callID = reactor.callLater(5, f)callID.cancel()