[src] Fix incorrect invocation of mutex in nnet-batch-compute code (#2932)

Author: danpovey

src/nnet3/nnet-batch-compute.cc

@@ -135,7 +135,7 @@ NnetBatchComputer::GetHighestPriorityComputation(
  int32 *minibatch_size_out,
  std::vector<NnetInferenceTask*> *tasks) {
  tasks->clear();
- std::unique_lock<std::mutex>(mutex_);
+ std::unique_lock<std::mutex> lock(mutex_);
  MapType::iterator iter = tasks_.begin(), end = tasks_.end(),
  best_iter = tasks_.end();
  double highest_priority = -std::numeric_limits<double>::infinity();

src/nnet3/nnet-compute.h

@@ -119,7 +119,7 @@ class NnetComputer {
 
  // Version of GetOutput that calls Swap(), destroying the output stored inside
  // this object. You should probably not use this if you plan to call
- // Backward() on the same NnetComputer object, or it's a recurret
+ // Backward() on the same NnetComputer object, or it's a recurrent
  // computation-- it may lead to a crash.
  void GetOutputDestructive(const std::string &output_name,
  CuMatrix<BaseFloat> *output);