@Override
  public void setStateChangeListener(SchedulerStateChangeListener listener) {
    this.listener = listener;
  }
Scheduler class invoked by the leader to check if the barrier has completed.
Checks every 15 seconds.
The leader polls the Azure processor table in order to track this.
The barrier is completed if all processors that are listed alive on the blob, have entries in the Azure table with the new job model version.
All time units are in SECONDS.
samza-azure/src/main/java/org/apache/samza/coordinator/scheduler/LeaderBarrierCompleteScheduler.java