Add support to have an option for both etcd and master to share a single load balancer

[samdgz]

When load balancer resources are limited in a single bmc tenancy, it'll limit the total number of k8s clusters that can be set up in a team to be used in testing and development, if every installation requires two load balancers, one for etcd, and one for the masters.

[jrosinsk]

There is now a flag to disable the etcd load balancer. etcd_lb_enabled="false"

Although this doesn't quite combine them, it does allow for running a cluster with only a single load balancer resource.