message: Fix issue where converted data is freed before it is downloaded
  Summary:
  Previously the contents of the buffers were being freed before they
  were being downloaded
  Test Plan: existing tests - 64 bit test was occasionally failing
  Reviewers: georgep
diff: @@ -770,7 +770,6 @@ StatusOr<se::DeviceMemoryBase> PoplarExecutor::ExecuteEngine(
  tc->on_device = true;
  tc->input_handle = arg.first;
  - tc->converted_data.clear();
  if (current_config_.profiling().enable_io_trace()) {
  AddEventRecord(
  @@ -781,6 +780,11 @@ StatusOr<se::DeviceMemoryBase> PoplarExecutor::ExecuteEngine(
  }
  current_engine_->run(1);
  +
  + for (auto arg : arg_map) {
  + TensorControl* tc = arg.second.tc;
  + tc->converted_data.clear();
  + }
  }
  } catch (std::logic_error e) {
  return tensorflow::errors::Internal("Poplar host write error ",
  