message: fix threadsan issue
diff: @@ -321,8 +321,8 @@ unique_ptr<BufferHandle> BufferManager::Pin(shared_ptr<BlockHandle> &handle) {
  void BufferManager::AddToEvictionQueue(shared_ptr<BlockHandle> &handle) {
  D_ASSERT(handle->readers == 0);
  handle->eviction_timestamp++;
  - queue->q.enqueue(make_unique<BufferEvictionNode>(weak_ptr<BlockHandle>(handle), handle->eviction_timestamp));
  PurgeQueue();
  + queue->q.enqueue(make_unique<BufferEvictionNode>(weak_ptr<BlockHandle>(handle), handle->eviction_timestamp));
  }
  void BufferManager::PurgeQueue() {
  @@ -336,6 +336,7 @@ void BufferManager::PurgeQueue() {
  if (!handle) {
  continue;
  } else {
  + lock_guard<mutex> lock(handle->lock);
  queue->q.enqueue(move(node));
  break;
  }
  