Update gce quickstart to use CLUSTER_PREFIX always
Update gce quickstart to use CLUSTER_PREFIX always

dghubble/bootkube,hongchaodeng/bootkube,kubernetes-incubator/bootkube,ericchiang/bootkube,diegs/bootkube,dghubble/bootkube,kubernetes-incubator/bootkube,diegs/bootkube,ericchiang/bootkube,kubernetes-incubator/bootkube,hongchaodeng/bootkube,hongchaodeng/bootkube,diegs/bootkube,ericchiang/bootkube,dghubble/bootkube