kubeadm upgrade apply now is able to utilize all possible combinations
of version argument, including labels (latest, stable-1.8, ci/latest-1.9)
as well as specific builds (v1.8.0-rc.1, ci/v1.9.0-alpha.1.123_01234567889)
As side effect, specifying exact build to deploy from CI area is now also
possible in kubeadm init command.
Fixes: kubernetes/kubeadm#451
Allow to specify a node-name instead of relaying in `os.Hostname()`
This is useful where kubelet use the name given by the cloud-provider to
register the node.
Partially fix: kubernetes/kubeadm#64
