@Override
  public void shutdown() {
    LOG.info("Shutting down JMVersionUpgradeScheduler Scheduler.");
    scheduler.shutdownNow();
  }
Scheduler invoked by each processor to check for job model version upgrades on the blob.
Checks every 5 seconds.
The processor polls the leader blob in order to track this.
All time units are in SECONDS.
samza-azure/src/main/java/org/apache/samza/coordinator/scheduler/JMVersionUpgradeScheduler.java