Load balancer for masters in digitalocean

[tayzlor]

In AWS we use an ELB to balance the traffic to the master API servers. Digitalocean doesn't have native load balancing solution so we would need an alternative solution to this if we want to support HA API server in DO.

See https://github.com/Capgemini/kubeform/blob/master/roles/kube-master/defaults/main.yml#L6