Fixed kube-up.sh to point to the right place.

With recent changes in apiserver, URL.Path == "/" simply returns http.StatusNotFound, instead of index.html anymore. But kube-up.sh still points to "/" at the end of building a new cluster. Fixed kube-up.sh to point to the right place.

I'm just saying it's redundant to specify both, since the mux will route both to the same place.