message: test: fixing a downstream tsan failure
  Adding a lock for checking response completion since as far as tsan can tell it's possibly accessed by the main thread and test thread simultaneously.
  Risk Level: Low (test only)
  Testing: ran idle_timeouts_test with internal tsan
  Docs Changes: n/a
  Release Notes: n/a
diff: @@ -43,7 +43,10 @@ public:
  uint64_t bodyLength() { return body_.length(); }
  Buffer::Instance& body() { return body_; }
  - bool complete() { return end_stream_; }
  + bool complete() {
  + Thread::LockGuard lock(lock_);
  + return end_stream_;
  + }
  void encode100ContinueHeaders(const Http::HeaderMapImpl& headers);
  void encodeHeaders(const Http::HeaderMapImpl& headers, bool end_stream);
  void encodeData(uint64_t size, bool end_stream);
  