This replaces kube-master with kube_control_plane 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.
NOTE: The reason why this changes it to kube_control_plane not
kube-control-plane is for valid group names on ansible.
[1]: https://github.com/kubernetes/enhancements/blob/master/keps/sig-cluster-lifecycle/kubeadm/2067-rename-master-label-taint/README.md#motivation
Now the `kubespray-aws-inventory.py` script always set a node_labels key
to ansible_host.
When AWS instance did not set property labels, it would be an empty
string.
The TASK `Write kubelet config file (kubeadm or non-kubeadm)` will
failed with a msg:
`AnsibleUndefinedVariable: 'unicode object' has no attribute 'items'`.
