message: stats: fix scope timer prefix
  Regresion from I'm in the process of rewriting all of the scope stuff
  currently so I'm not going to bother with tests. I will add tests in the real
  change.
diff: @@ -10,10 +10,10 @@ public:
  // Stats::Scope
  void deliverHistogramToSinks(const std::string& name, uint64_t value) override {
  - parent_.deliverHistogramToSinks(name, value);
  + parent_.deliverHistogramToSinks(prefix_ + name, value);
  }
  void deliverTimingToSinks(const std::string& name, std::chrono::milliseconds ms) {
  - parent_.deliverTimingToSinks(name, ms);
  + parent_.deliverTimingToSinks(prefix_ + name, ms);
  }
  Counter& counter(const std::string& name) override;
  