python-common/rgw: fix get_realm_tokens returning empty result for realms with a secondary zone
Issue: The Export Multi-site Realm Token feature in the Dashboard showed no token and no realm details for any realm that had a secondary zone configured (i.e. the realm had been replicated to another cluster). The API endpoint GET /api/rgw/realm/get_realm_tokens returned an empty list or raised a 500 Internal Server Error.