Automatic merge from submit-queue
Centos provider: generate SSL certificates for etcd cluster.
**What this PR does / why we need it**:
Support secure etcd cluster for centos provider, generate SSL certificates for etcd in default. Running it w/o SSL is exposing cluster data to everyone and is not recommended. [#39462](https://github.com/kubernetes/kubernetes/pull/39462#issuecomment-271601547)
/cc @jszczepkowski @zmerlynn
**Release note**:
```release-note
Support secure etcd cluster for centos provider.
```
Deprecation Notice: This directory has entered maintenance mode and will not be accepting new providers. Please submit new automation deployments to kube-deploy. Deployments in this directory will continue to be maintained and supported at their current level of support.
The scripts and data in this directory automate creation and configuration of a Kubernetes cluster, including networking, DNS, nodes, and master components.