MasterConfiguration should be changed to support more recent k8

[rvasilev]

There were a number of changes in kubeadm configuration file structure between 1.9 and 1.11 (kubernetes/kubernetes#63788) and 1.11 to 1.12 (kubernetes/kubernetes#65945), because of this changing of k8 version in the source (#162, #197) will not work.

The easiest workaround IMO - to bump apiVersion: kubeadm.k8s.io/v1alpha2, set #162 to 1.11, create cluster and after that apply kubeadm upgrade to 1.12.

The more flexible way may be to templetize master.yaml or to provide different config generator function based on k8 version.

hetzner-kube/pkg/clustermanager/configs.go

Lines 8 to 35 in 034fefa

	//GenerateMasterConfiguration generate the kubernetes config for master
	func GenerateMasterConfiguration(masterNode Node, masterNodes, etcdNodes []Node) string {
	masterConfigTpl := `apiVersion: kubeadm.k8s.io/v1alpha1
	kind: MasterConfiguration
	api:
	advertiseAddress: %s
	networking:
	podSubnet: 10.244.0.0/16
	apiServerCertSANs:
	- %s
	- 127.0.0.1
	`
	etcdConfig := `etcd:
	endpoints:`
	masterConfig := fmt.Sprintf(masterConfigTpl, masterNode.PrivateIPAddress, masterNode.IPAddress)
	for _, node := range masterNodes {
	masterConfig = fmt.Sprintf("%s%s\n", masterConfig, " - "+node.PrivateIPAddress)
	}
	if len(etcdNodes) > 0 {
	masterConfig = masterConfig + etcdConfig + "\n"
	for _, node := range etcdNodes {
	masterConfig = fmt.Sprintf("%s%s\n", masterConfig, " - http://"+node.PrivateIPAddress+":2379")
	}
	}
	return masterConfig
	}

And the best way will be to support latest and previous stable version of k8s.

[xetys]

This has happened in #243