Clientset.Coordination is deprecated. We are meant to use the specific
version of the client: CoordinationV1beta1. Clientset.Coordination is
going to be removed in future versions of the client API.
When setting up the http server we return a cancel function to close all
the listeners down.
The issue here is we set the cancel function to nil and thereby cause a
panic when there is an error and the `defer` attempts to call cancel.
This fix just don't set a named return value for the cancel function to
make sure we don't overwrite it with a `return nil, err`.
This ensures that the `defer` can still call `cancel()`.
This cleans up the CLI code significantly.
Also makes some of this re-usable for providers who want to do so.
This also removes the main.go from the top of the tree of the repro,
instead moving it into cmd/virtual-kubelet.
This allows us to better utilize the package namespace (and e.g. mv the
`vkubelet` package to the top of the tree).
