@Override
  public void shutdown() throws InterruptedException {
    logger.info("Shutting down FileCopyBasedReplicationSchedulerImpl");
    isRunning = false;
    fileCopyBasedReplicationThreadPoolManager.shutdown();
    fileCopyBasedReplicationThreadPoolManagerThread.join();
    logger.info("FileCopyBasedReplicationSchedulerImpl shutdown");
  }
Find the replicas that are starved for hydration. Return a list of Replicas
which are stuck in hydration for more than the configured values.
@return the list of {@link ReplicaId} that are starved for hydration.
ambry-file-transfer/src/main/java/com/github/ambry/filetransfer/FileCopyBasedReplicationSchedulerImpl.java