capm3 workload cluster upgrade fails in CI

Summary

When management cluster update job succeed in capm3, workload cluster update is systematically failing, with the same error, as in:

https://gitlab.com/sylva-projects/sylva-core/-/jobs/7898686916

We can see that ironic-python-agent is failing to reach ironic api:

2024-09-23 22:47:41 ::  [   64.737976] ironic-python-agent[634]: 2024-09-23 22:47:40.449 634 DEBUG ironic_python_agent.ironic_api_client [-] Looking up node with addresses '52:54:00:55:55:04,02:66:6d:02:7f:1f,52:54:00:44:44:04,02:66:6d:02:7f:1f' and UUID None at ['https://192.168.100.2:6385'] _do_lookup /usr/lib/python3.11/site-packages/ironic_python_agent/ironic_api_client.py:227[00m
2024-09-23 22:47:41 ::  [   64.741829] ironic-python-agent[634]: [0;1;38;5;185m2024-09-23 22:47:40.447 634 WARNING root [-] Invalid ipmitool output [0m
2024-09-23 22:47:41 ::  [   64.743289] ironic-python-agent[634]: 2024-09-23 22:47:40.448 634 INFO root [-] Inventory collected in 1.36 second(s)
2024-09-23 22:47:44 ::  [   67.505834] NetworkManager[710]: <info>  [1727131663.2262] manager: startup complete
2024-09-23 22:47:44 ::  [   67.808645] ironic-python-agent[634]: 2024-09-23 22:47:43.525 634 ERROR ironic_python_agent.ironic_api_client [-] An error occurred while attempting to discover the available Ironic API versions, falling back to using version 1.31: requests.exceptions.ConnectionError: HTTPSConnectionPool(host='192.168.100.2', port=6385): Max retries exceeded with url: / (Caused by NewConnectionError('<urllib3.connection.HTTPSConnection object at 0x7f0ebb7e2d10>: Failed to establish a new connection: [Errno 113] EHOSTUNREACH'))
2024-09-23 22:47:44 ::  [   67.814109] ironic-python-agent[634]: 2024-09-23 22:47:43.525 634 ERROR ironic_python_agent.ironic_api_client Traceback (most recent call last):

[...]

2024-09-23 22:47:44 ::  [   67.864402] ironic-python-agent[634]: 2024-09-23 22:47:43.525 634 ERROR ironic_python_agent.ironic_api_client                        ^^^^^^^^^^^^^^^^
2024-09-23 22:47:44 ::  [   67.866196] ironic-python-agent[634]: 2024-09-23 22:47:43.525 634 ERROR ironic_python_agent.ironic_api_client   File "/usr/lib/python3.11/site-packages/urllib3/connection.py", line 186, in _new_conn
2024-09-23 22:47:44 ::  [   67.868393] ironic-python-agent[634]: [0;1;31m2024-09-23 22:47:43.525 634 ERROR ironic_python_agent.ironic_api_client [-] An error occurred while attempting to discover the available Ironic API versions, falling back to using version 1.31: requests.exceptions.ConnectionError: HTTPSConnectionPool(host='192.168.100.2', port=6385): Max retries exceeded with url: / (Caused by NewConnectionError('<urllib3.connection.HTTPSConnection object at 0x7f0ebb7e2d10>: Failed to establish a new connection: [Errno 113] EHOSTUNREACH'))