message: Avoid excessive lock contention in CCheckQueue::Add
diff: @@ -166,13 +166,16 @@ public:
  //! Add a batch of checks to the queue
  void Add(std::vector<T>& vChecks)
  + {
  {
  LOCK(m_mutex);
  for (T& check : vChecks) {
  - queue.push_back(T());
  + queue.emplace_back();
  check.swap(queue.back());
  }
  nTodo += vChecks.size();
  + }
  +
  if (vChecks.size() == 1)
  m_worker_cv.notify_one();
  else if (vChecks.size() > 1)
  