Refactor images layer to prep for adding Glance V2 support

This refactoring patch lays the initial groundwork for Glance V2
API support by moving the GlanceClientWrapper and some associated
functions and configuration into a new package which will later
contain drivers for Glance V1 and V2.

Change-Id: I7c2d42daff3ec939e5ae90e13dc753f403afb6fd
Implements: bp use-glance-v2-api
Add driver for Glance v1

Establishes the driver architecture and adds implementation for
Glance API v1 driver and tests.

Note that this does NOT make use of the driver yet.

Implements bp use-glance-v2-api

Change-Id: I6dd3f5df7bfc0daa32fc5515f28b3937dc5ab5fa