Switch from cli configuration to kubelet.conf

[ijc]

With the bump to v1.10 in #70 Kubelet is now complaining:

# Flag --pod-manifest-path has been 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.
# Flag --allow-privileged has been deprecated, will be removed in a future version
# Flag --cluster-dns has been 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.
# Flag --cluster-domain has been 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.
# Flag --cgroups-per-qos has been 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.
# Flag --enforce-node-allocatable has been 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.
# Flag --cadvisor-port has been deprecated, The default will change to 0 (disabled) in 1.12, and the cadvisor port will be removed entirely in 1.13
# Flag --kube-reserved-cgroup has been 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.
# Flag --system-reserved-cgroup has been 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.
# Flag --cgroup-root has been 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.

It appears (on a quick look) that the way to provide kubelet.conf when using kubeadm is to use the KubeletConfiguration field in kubeadm.conf which has the same KubeletConfiguration type as kubelet.conf.

Using this will mean reworking a bunch of the setup stuff in kubelet.sh so it's not entirely trivial, especially when considering there is the option to provide the config via metadata.