- Factor out token constants to kubeadmconstants.
- Move cmd/kubeadm/app/util/{,token/}tokens.go
- Use the token-id, token-secret, etc constants provided by the bootstrapapi package
- Move cmd/kubeadm/app/master/tokens.go to cmd/kubeadm/app/phases/token/csv.go
This refactor basically makes it possible to hook up kubeadm to the BootstrapSigner controller later on
Automatic merge from submit-queue
Implemented file and HTTPS based discovery for kubeadm
**What this PR does / why we need it**:
This PR implements both file and HTTPS based discovery for `kubeadm`.
**Which issue this PR fixes**:
fixes https://github.com/kubernetes/kubeadm/issues/93
fixes https://github.com/kubernetes/kubeadm/issues/94
**Special notes for your reviewer**:
I'd like to add some tests but 'm sure `kubeconfig` loading is already covered by other tests in `clientcmd` package.
/cc @luxas @pipejakob
