Automatic merge from submit-queue
Check for EmptyConfig errors when trying to use in-cluster config
By removing the default "localhost:8080" behavior several paths in
client config began returning err == ErrEmptyConfig rather than err ==
nil. The code checking for in cluster config was wrong - the logic
should be:
1. If loading the underlying config returns a non-empty error, fail
2. If the underlying config is not equal to the default config,
return that config (it has user input)
3. If it is possible to use in-cluster config, do so
4. Otherwise return the default config (and or default EmptyConfig
error).
Fixes#31910 @thockin @lavalamp @deads2k. We introduced EmptyConfig a very long time ago, but until I removed the "localhost:8080" Kubernetes was not actually exposing it (OpenShift relies on it since we don't set an insecure default). This properly falls through to in-cluster config in the described conditions.
```release-note
Some components like kube-dns and kube-proxy could fail to load the service account token when started within a pod. Properly handle empty configurations to try loading the service account config.
```
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