Enhancement deuce context swift storage url

- Stores the storage_url in the Deuce Context under deuce.context.openstack.swift.storage_url
- Fixes the mocking for Swift Client so that it is enabled via a single variable in config.py so the user does not need to modify test code to turn it on/off.

Depends on PR #82 

JIRA #CBDEUCE-153
I think we should remove the dependency on python-keystoneclient. It's incredibly big and headache-inducing just so we can run our tests. That's really orthogonal to this PR, so I don't think it should hold it up, but I will create a separate story to remove that dependency.