[WIP] Add haproxy cookbook
More WIP haproxy
Add helpers for WIP
Always install haproxy on cluster nodes

If it's not done early enough, then some nodes will not have it
installed when the resource is first declared and these nodes will have
this error:
warning: services_os_action_execute: Cannot execute '/etc/init.d/haproxy': No such file or directory (2)

This is fixable with "crm resource refresh", but we might as well just
install it.
WIP haproxy
Allow a retry when creating primitive for haproxy

This helps work around "crashes" due to races where two nodes create the
primitive at the same time when it wasn't created yet (only one can
obviously succeed).
Add PacemakerHelper.cluster_name helper
Change PacemakerHelper.haproxy_servers to avoid never-growing nodes

Due to node saving in cookbooks, we were saving nodes that were
containing all the info about other nodes. And that was growing
exponentially.
Add PacemakerHelper.cluster_nodes helper