code: boolean isStale(ServiceNamespace namespace, long[] newVersions, int replicaIndex) {
          return getFragmentVersions(namespace).isStale(newVersions, replicaIndex);
      }
docs: Returns whether given replica version is behind the current version or not.
  @param namespace replica namespace
  @param newVersions new replica versions
  @param replicaIndex replica index
  @return true if given version is stale, false otherwise