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
For the unit test purposes, we are still using disk to mock swift right? 
We just change up the swift module we load, if we want to test against a real swift instance, correct?
Please correct me If I'm wrong.