Cluster with TLS bootstrap disabled fails to start self-hosted Kubelet

[surajssd]

The self-hosted kubelet has a dependency on a file to exist at /var/lib/kubelet/kubeconfig. This was added during the cert rotation feature.

On a cluster that has TLS bootstrap disabled there is no file at /var/lib/kubelet/kubeconfig so the self-hosted kubelet fails to come up. The current workaround is to create an empty file at /var/lib/kubelet/kubeconfig. The ideal solution is that we create a empty file by default if enable_tls_bootstrap is set to false.

And the best solution is to deprecate enable_tls_bootstrap with an upgrade paths that have disabled enable_tls_bootstrap.

[surajssd]

Related: https://github.com/kinvolk/lokomotive/issues/1468