add named port for frontend-external so that istio metrics aren't blocked
add named port for frontend-external so that istio metrics aren't blocked

GoogleCloudPlatform/microservices-demo,GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/microservices-demo,GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/microservices-demo,GoogleCloudPlatform/microservices-demo,GoogleCloudPlatform/microservices-demo,GoogleCloudPlatform/microservices-demo,GoogleCloudPlatform/microservices-demo,GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/cloud-ops-sandbox