Improve test_list_active_clients()
Improve test_list_active_clients()

Now the assertion "the same country should be listed only once" is verified.

codeeu/coding-events,michelesr/coding-events,michelesr/coding-events,codeeu/coding-events,codeeu/coding-events,codeeu/coding-events,codeeu/coding-events,michelesr/coding-events,michelesr/coding-events,michelesr/coding-events