CF template: external load balancer template fails due to health check

When deploying the [external load balancer templates](https://github.com/GoogleCloudPlatform/deploymentmanager-samples/tree/master/community/cloud-foundation/templates/external_load_balancer) with `healthCheck` set to the `selfLink` of a previously defined health check resource (eg.: `$(ref.my-health-check.selfLink)`), I get the following error:

```
Invalid value for field 'resource.healthChecks[0]':
'https://www.googleapis.com/compute/v1/projects/xxx/global/httpHealthChecks/my-health-check'.
This TCP/UDP/SSL backend service only supports HealthCheck"
```

I've also tried setting `healthCheck` to the hardcoded self link (`projects/xxx/global/httpHealthChecks/my-health-check`) but the error persists.