message: Add lock in Random()
diff: @@ -196,8 +196,8 @@ class SamplingDatasetOp : public UnaryDatasetOpKernel {
  private:
  std::unique_ptr<IteratorBase> input_impl_ GUARDED_BY(mu_);
  - float Random()
  - EXCLUSIVE_LOCKS_REQUIRED(mu_) {
  + float Random() {
  + mutex_lock l(mu_);
  num_random_samples_++;
  auto out = generator_.RandFloat();
  return out;
  