pkg/asset/internal: label key naming consistency
pkg/asset/internal: label key naming consistency

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