This replaces KUBE_MASTERS with KUBE_CONTROL_HOSTS because of [1]:
```
The Kubernetes project is moving away from wording that is
considered offensive. A new working group WG Naming was created
to track this work, and the word "master" was declared as offensive.
A proposal was formalized for replacing the word "master" with
"control plane". This means it should be removed from source code,
documentation, and user-facing configuration from Kubernetes and
its sub-projects.
```
[1]: https://github.com/kubernetes/enhancements/blob/master/keps/sig-cluster-lifecycle/kubeadm/2067-rename-master-label-taint/README.md#motivation
This variable was added as KUBE_MASTERS_MASTERS. That's probably a typo.
Remove the redundant `_MASTERS` suffix. Also, document the variable in the
help message.
inventory_builder creates hosts.yaml file with hostnames like "node1",
"node2", etc. Even if specifying override_system_hostname=false, the
output of "kubectl get nodes" shows those hostnames ("node1", etc.)
without using actual hostnames.
To solve this issue, this adds an option USE_REAL_HOSTNAME to get
actual hostnames when creating hosts.yaml file instead of "node1", etc.
* add to inventory.py script ability to indicate ip ranges
* add test for range2ip function for inventory.py script
some fixes
* add negative test for range2ip function for inventory.py script
This does not address per-node certs and scheduler/proxy/controller-manager
component certs which are now required. This should be handled in a
follow-up patch.
Also adds calico-rr group if there are standalone etcd nodes.
Now if there are 50 or more nodes, 3 etcd nodes will be standalone.
If there are 200 or more nodes, 2 kube-masters will be standalone.
If thresholds are exceeded, kube-node group cannot add nodes that
belong to etcd or kube-master groups (according to above statements).
