Some of the tests are very slow

```
============================= slowest 10 durations =============================
31.21s call tests/test_images.py::test_build_from_remote_tar
23.38s call tests/test_containers.py::test_restart
17.41s call tests/test_images.py::test_build_from_remote_file
12.25s setup tests/test_configs.py::test_config_list_with_filter
10.12s call tests/test_integration.py::test_attach_nontty_wait_for_exit
6.74s call tests/test_containers.py::test_run_container_with_missing_image
6.44s teardown tests/test_nodes.py::test_node_update
5.47s call tests/test_containers.py::test_run_existing_container
5.12s call tests/test_containers.py::test_stop_with_short_http_timeout
4.60s setup tests/test_secrets.py::test_secret_list_with_filter
================== 162 passed, 2 xfailed in 233.88s (0:03:53) ==================
```