cloud_to_prod and cloud_to_prod_auth interop tests are flaky against "default" and "gateway_v4".

Seen at https://grpc-testing.appspot.com/job/gRPC_interop_pull_requests/13464/ and https://grpc-testing.appspot.com/job/gRPC_interop_pull_requests/13477/.

They all seem to be reporting connection failures