Fix cassandra vault stats, use dicts instead of tuples. 

This patch does a couple of things:

1) Fixes cassandra driver so it can run against a real cassandra instance. This was a regression caused by over overly liberal mocking framework.
2) Adds the ability to use dictionary-based arguments in our mocker.
3) Changes all arguments to be dictionary-based. 

Closes: CBDEUCE-154
Closes: CBDEUCE-141.


Honestly, I see no value exposing any of the "internal" stuff through the user-facing API.