Update private registry documentation
Update private registry documentation

This lets developers know that they have to restart localkube/kubelet after modifying the docker credentials
r2d4/minikube,warmchang/minikube,warmchang/minikube,kubernetes/minikube,dalehamel/minikube,dlorenc/minikube,dlorenc/minikube,dlorenc/minikube,kubernetes/minikube,dalehamel/minikube,dims/minikube,dlorenc/minikube,warmchang/minikube,kubernetes/minikube,warmchang/minikube,warmchang/minikube,dims/minikube,r2d4/minikube,kubernetes/minikube,r2d4/minikube,aaron-prindle/minikube,kubernetes/minikube,dlorenc/minikube,warmchang/minikube,dims/minikube,kubernetes/minikube,dalehamel/minikube,aaron-prindle/minikube,dlorenc/minikube,kubernetes/minikube,warmchang/minikube,aaron-prindle/minikube,dlorenc/minikube,dlorenc/minikube