Add a 500 ms sleep when queuing futures, just in case

cpp/ci_logic.cpp

@@ -697,6 +697,7 @@ std::string CiLogic::queue_pull_tarball(std::vector<std::shared_ptr<PackageConf>
                     encountered_items[r->package->name] = new_item;
                 }
             }));
+            std::this_thread::sleep_for(std::chrono::milliseconds(500));
         }
         for (auto& future : futures) future.get();
         msg = "Succeeded";