message: Avoid using the Graph owned FunctionLibraryDefinition in GraphMgr
  This is part of a series of change intended to decouple the FunctionLibraryDefinition
  from the Graph entirely.
diff: @@ -179,7 +179,7 @@ Status GraphMgr::InitItem(
  return PartitionOptions::kIllegalIncarnation;
  }
  };
  - popts.flib_def = &graph.flib_def();
  + popts.flib_def = item->lib_def.get();
  popts.control_flow_added = true;
  popts.scheduling_for_recvs = graph_options.enable_recv_scheduling();
  TF_RETURN_IF_ERROR(Partition(popts, &graph, &partitions));
  