Store cgroup driver in kubeadm configuration file for kubernetes 1.12+

[jorhett]

$  kubelet --help |grep cgroup
      --cgroup-driver string

Driver that the kubelet uses to manipulate cgroups on the host.
Possible values: 'cgroupfs', 'systemd' (default "cgroupfs")
(DEPRECATED: This parameter should be set via the config file specified by the Kubelet's --config flag.
 See https://kubernetes.io/docs/tasks/administer-cluster/kubelet-config-file/ for more information.)

This PR also includes major refactoring to make YAML template build tests less prescriptive and less likely to fail due to minor changes that aren't actual failures.

[davejrt]

LGTM