synchronized FindToken getTokenToPersist() {
    if (time.milliseconds() - timeCandidateSetInMs > tokenPersistIntervalInMs) {
      // candidateTokenToPersist is now safe to be persisted.
      tokenSafeToPersist = candidateTokenToPersist;
    }
    return tokenSafeToPersist;
  }
get the token to persist. Returns either the candidate token if enough time has passed since it was
set, or the last token again.
ambry-replication/src/main/java/com/github/ambry/replication/RemoteReplicaInfo.java