Merge branch 'master' into idempotency2

README.md

contrib/terraform/openstack/group_vars

contrib/terraform/openstack/kubespray.tf

docs/coreos.md

inventory/group_vars/k8s-cluster.yml

requirements.txt

roles/docker/templates/docker-options.conf.j2

roles/etcd/tasks/check_certs.yml

roles/etcd/tasks/gen_certs_script.yml

roles/kargo-defaults/defaults/main.yaml

roles/kubernetes/master/defaults/main.yml

roles/kubernetes/master/tasks/main.yml

roles/kubernetes/master/tasks/post-upgrade.yml

roles/kubernetes/master/tasks/pre-upgrade.yml

...tes/master/templates/manifests/kube-apiserver.manifest.j2

roles/kubernetes/preinstall/tasks/resolvconf.yml

roles/kubernetes/secrets/tasks/check-tokens.yml

roles/kubernetes/secrets/tasks/main.yml