Move SolidFire driver from httplib to requests

Move SolidFire driver from httplib to requests

The SolidFire driver has been pretty static for a number of
years now, this change is to move from httplib for API calls
to requests.  There are a number of advantages to this, including
performance, simplicity and ability to add things like ssl support
easily.

In addtion this change removes the confusing looping/retry mechanisms
that were in the issue_api_request method and replaces it with a
retry decorator for the exceptions we're interested in retrying.

Finally, I realize that my unit tests suck!  That will be one of the
follow up items after a bit more clean up in the driver.

Change-Id: Icc4cf601bffddb057f35537f3870c45dd5eb67cc