message: backend: unsubscribe correct subscription
  This was a copy&paste mistake.
diff: @@ -178,7 +178,7 @@ public:
  std::lock_guard<std::mutex> lock(_subscribe_mutex);
  if (!*is_finished && !writer->Write(rpc_mode_response)) {
  - _camera.subscribe_status(nullptr);
  + _camera.subscribe_mode(nullptr);
  *is_finished = true;
  stream_closed_promise.set_value();
  }
  @@ -307,7 +307,7 @@ public:
  std::lock_guard<std::mutex> lock(_subscribe_mutex);
  if (!*is_finished && !writer->Write(rpc_video_stream_info_response)) {
  - _camera.subscribe_status(nullptr);
  + _camera.subscribe_video_stream_info(nullptr);
  *is_finished = true;
  stream_closed_promise.set_value();
  }
  @@ -336,7 +336,7 @@ public:
  std::lock_guard<std::mutex> lock(_subscribe_mutex);
  if (!*is_finished && !writer->Write(rpc_capture_info_response)) {
  - _camera.subscribe_status(nullptr);
  + _camera.subscribe_capture_info(nullptr);
  *is_finished = true;
  stream_closed_promise.set_value();
  }
  @@ -566,7 +566,7 @@ public:
  std::lock_guard<std::mutex> lock(_subscribe_mutex);
  if (!*is_finished && !writer->Write(rpc_current_setting_response)) {
  - _camera.subscribe_status(nullptr);
  + _camera.subscribe_current_settings(nullptr);
  *is_finished = true;
  stream_closed_promise.set_value();
  }
  @@ -637,7 +637,7 @@ public:
  std::lock_guard<std::mutex> lock(_subscribe_mutex);
  if (!*is_finished && !writer->Write(rpc_setting_options_response)) {
  - _camera.subscribe_status(nullptr);
  + _camera.subscribe_possible_setting_options(nullptr);
  *is_finished = true;
  stream_closed_promise.set_value();
  }
  