initial HA support (WIP)

- mostly copy&paste from nova_dashboard
- chef stuff: missing integration into radosgw_apache and radosgw_keystone recipes
I know you wanted this, but in other recipes we usually have ```default["component"]["ha"]["more_details"]```, see e.g. ceilometer.
And for ports, haproxy_servers_for_service expects ```server_node[name][:ha][:ports][ports_key]``` https://github.com/crowbar/barclamp-pacemaker/blob/master/chef/cookbooks/crowbar-pacemaker/libraries/helpers.rb#L181