tests: parameterize prefix for GCE assets in conformance tests
tests: parameterize prefix for GCE assets in conformance tests

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