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 hope we dn't have testing related setting in config.py, which should be for production only.  We may provide instructions on modifying config.py in a readme, or have testing settings in another configuration py file, or let unit-tests modify config.py for their use, which is like what I implementated.