Add empty swiftnode stanza for now

Adding an empty swiftnode stanza so that CI will work again. Will
eventually get the CI building out swift cluster as well. Blocker
at the moment is getting haproxy role more modular.
Move from indexed swiftnodes to swiftnode_primary

If you try to index into an empty group, you will (understandably) get a
python stacktrace. So, instead of indexing in, use another host class.
Merge pull request #306 from craigtracey/swiftnodeci

Add empty swiftnode stanza for now