We can remove all uses of `dockershim` from `cmd/kubelet`, by just
passing the docker options to the kubelet in their pure form, instead of
using them to create a `dockerClientConfig` (which is defined in
dockershim). We can then construct the `dockerClientConfig` only when we
actually need it.
Extract a `runDockershim` function into a file outside of `kubelet.go`.
We can use build tags to compile two separate functions... one which
actually runs dockershim and one that is a no-op.