Issue with private cluster endpoint

When setting `enable_private_nodes` to false on a private cluster, this error comes up:

```
 95:   cluster_output_endpoint = var.deploy_using_private_endpoint ? google_container_cluster.primary.private_cluster_config.0.private_endpoint : google_container_cluster.primary.private_cluster_config.0.public_endpoint
```

Introduced in 018c6fb93dc90065e828cc066eedb7a35bd0fec1