More haproxy work
Fix bugs in WIP
Move DNS synchronization to a different helper

We don't want to do this several times if we have more than one clusters
involved.
Add helpers to get hostnames for OpenStack endpoints

This is common code that all barclamps need, so a helper is a good
thing.
Integrated cluster selection into node selector
Merge pull request #16 from tboerger/feature/ha-interface

Integrated cluster selection into node selector
Merge pull request #15 from vuntz/haproxy

[WIP] HA with HAProxy