Test `unload_on_kill_activate_as_group` fails on jazzy/testing

[christophfroehlich]

2024-09-13T02:29:16.7694364Z 9: /home/runner/work/ros2_control/ros2_control/.work/target_ws/src/ros2_control/controller_manager/test/test_spawner_unspawner.cpp:347: Failure
2024-09-13T02:29:16.7694540Z 9: Expected equality of these values:
2024-09-13T02:29:16.7694700Z 9:   cm_->get_loaded_controllers().size()
2024-09-13T02:29:16.7694790Z 9:     Which is: 2
2024-09-13T02:29:16.7694871Z 9:   0ul
2024-09-13T02:29:16.7694961Z 9:     Which is: 0
2024-09-13T02:29:16.7704118Z 9: 

see https://github.com/ros-controls/ros2_control/issues/1751 and https://github.com/ros-controls/ros2_control/actions/runs/10841825910/attempts/1