BZ #1173730 - allow separation of cluster and management networks

https://bugzilla.redhat.com/show_bug.cgi?id=1173730

Pacemaker and galera may now implement their internal cluster
communication over $pcmk_server_addrs/$pcmk_server_addrs which may be
defined as equivalent to or different from the management network
(defined by $lb_backend_server_addrs/$lb_backend_server_names).