Issues #562,#561,#560:

- No source of entropy in _get_nearest_mirrors_by_network_data()
- _get_nearest_mirrors_by_network_data() fails to exclude near-by private mirrors for extra options.
- Exclude the private mirrors from the mirrors list in the case of fallback behavior

The Azure mirrors have allowed list of arches

src/backend/api/handlers.py

@@ -135,9 +135,7 @@ def _is_additional_mirrors_suitable(
             mirrors=sorted_additional_mirrors,
             country=country,
         )[:LENGTH_CLOUD_MIRRORS_LIST - len(suitable_mirrors)]
-        suitable_mirrors.extend(
-            mirror['mirror'] for mirror in randomized_additional_mirrors
-        )
+        suitable_mirrors.extend(randomized_additional_mirrors)
     return suitable_mirrors