Automatic merge from submit-queue
support customize repository prefix of image through environment KUBE…
## Problem
kubeadm does not support customize repository prefix of image. this prevent us from using our own image repository to deploy k8s.
## Fix
make ```gcr.io/google_containers/ ``` be configurable.
ADD environment variable KUBE_REPO_PREFIX
Signed-off-by: yaoyao.xyy <yaoyao.xyy@alibaba-inc.com>
39e64fde8c