Do not return the cluster credentials when uploading a kubeconfig that already exists. Only return error message

[rajakshay]

If the kubeconfig already exists on hyperkube, and I try to re-upload it, it responds with 2 things:

1. The kubeconfig
2. The error message: {'message': 'Cluster cluster-name already exists'}

This is usually not an expected operation, but, I came across this while testing kubeconfig upload and download and re-trying those operation.

My problem is that I want to display this error message on failure, but, I do not want to display the kubeconfig. Also, the user asked to upload the kubeconfig, and not download it.

If I send the response to dev/null, I lose the error message as well. Would have been easier to handle this in code, but, unfortunately, I am using bash.