k8s cluster discovery incomplete

[stephen-soltesz]

When originally developed, k8s service discovery could iterate through zones b/c we created clusters in specific zones. Today, clusters can be created in a "region" with redundancy in zones. However, the k8s API server runs on a regional address now, so the following is not enough:

	return g.containerService.Projects.Zones.Clusters.List(g.project, zone).Context(ctx).Do()

Instead, we need to use something like:

	return g.containerService.Projects.Locations.Clusters.List(...).Context(ctx).Do()