message: camera: don't set mode if already correct
  The E90 camera doesn't like a mode to be set to what it's already set
  to.
diff: @@ -40,9 +40,15 @@ Camera::Mode get_mode(std::shared_ptr<Camera> camera)
  void set_mode(std::shared_ptr<Camera> camera, Camera::Mode mode)
  {
  + Camera::Mode mode_already_set = get_mode(camera);
  +
  // FIXME: this should not be required.
  std::this_thread::sleep_for(std::chrono::seconds(2));
  + if (mode == mode_already_set) {
  + return;
  + }
  +
  auto prom = std::make_shared<std::promise<void>>();
  auto ret = prom->get_future();
  