create_test_user_ns_with_mapping
test_ns = create_test_user_ns_with_mapping(test, parent_ns, mapped_kuid);
ns1 = create_test_user_ns_with_mapping(test, &init_user_ns, KUIDT_INIT(1000));
ns2 = create_test_user_ns_with_mapping(test, &init_user_ns, KUIDT_INIT(2000));
ns3 = create_test_user_ns_with_mapping(test, &init_user_ns, KUIDT_INIT(3000));