public ReplySender getReplySender(DistributionManager dm) {
    if (acker != null) {
      return acker;
    } else {
      return dm;
    }
  }
Get the next bit mask position while checking that the value should not exceed given maximum
value.
geode-core/src/main/java/org/apache/geode/distributed/internal/DistributionMessage.java