Revisit checkState() in HdfsTable#getTHdfsTable()

/**
   * Create a THdfsTable corresponding to this HdfsTable. If includeFileDesc is true,
   * then then all partitions and THdfsFileDescs of each partition should be included.
   * Otherwise, don't include any THdfsFileDescs, and include only those partitions in
   * the refPartitions set (the backend doesn't need metadata for unreferenced
   * partitions).
   */
  private THdfsTable getTHdfsTable(boolean includeFileDesc, Set<Long> refPartitions) {
    // includeFileDesc implies all partitions should be included (refPartitions == null).
    Preconditions.checkState(!includeFileDesc || refPartitions == null);