Use noTaintMaster in kubeadm.conf

[ijc]

With the switch to v1.10 in #70 we can now make use of https://github.com/kubernetes/kubernetes/pull/55479 and set noTaintMaster: true in kubeadm.conf instead of untainting after initialisation.

Perhaps also depends on #71?

[ijc]

This has changed in https://github.com/kubernetes/kubernetes/pull/64210 (will be in v1.12 AFAICT). A comment in there explains:

+	// Taints specifies the taints the Node API object should be registered with. If this field is unset, i.e. nil, in the `kubeadm init` process
+	// it will be defaulted to []v1.Taint{'node-role.kubernetes.io/master=""'}. If you don't want to taint your master node, set this field to an
+	// empty slice, i.e. `taints: {}` in the YAML file. This field is solely used for Node registration.
+	Taints []v1.Taint

Also related: https://github.com/kubernetes/kubernetes/pull/65068