Some domains, like ELBs, output a domain name with uppercase letters. To
accept these, we lowercase all arguments passed to ----apiserver-cert-extra-sans
Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
validate AdvertiseAddress in kubeadm init and other case
**What this PR does / why we need it**:
When using `kubeadm init --apiserver-advertise-address=****, `apiserver-advertise-address` can only be ipv4 or ipv6 address, if people use domain name in this field, will not use it and silently get hostIP.
Add a warning in this case.
**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixeskubernetes/kubeadm#590
**Special notes for your reviewer**:
**Release note**:
```release-note
NONE
```
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
