[hetzner] cluster-autoscaler addon missing HCLOUD_TOKEN environment variable

[bjornharrtell]

Summary

The cluster-autoscaler addon template does not inject the HCLOUD_TOKEN environment variable into the autoscaler pod when running on Hetzner. As a result, the autoscaler fails immediately on startup because it cannot authenticate with the Hetzner API.

Root cause

upup/models/cloudup/resources/addons/cluster-autoscaler.addons.k8s.io/k8s-1.15.yaml.template only has an env: block for AWS (AWS_REGION). There is no corresponding block for Hetzner.

The hcloud secret (containing token and network keys) is already created in kube-system by the CCM addon, so the credentials are available — they just aren't passed to the autoscaler container.

Impact

The kops-managed cluster-autoscaler addon is completely non-functional on Hetzner. Users must deploy the autoscaler manually with the correct environment variables.

Originally reported in #17543.

Fix

Add an else if (eq GetCloudProvider "hetzner") env block that sources HCLOUD_TOKEN and HCLOUD_NETWORK from the existing hcloud secret. Fix included in the PR that accompanies this issue.