private SchedulerStateChangeListener createLeaderLivenessListener() {
    return () -> {
      LOG.info("Existing leader died.");
      azureLeaderElector.tryBecomeLeader();
    };
  }
Creates a listener for LeaderLivenessCheckScheduler class.
Invoked when an existing leader dies. Enables the JC to participate in leader election again.
@return an instance of SchedulerStateChangeListener.
samza-azure/src/main/java/org/apache/samza/coordinator/AzureJobCoordinator.java