Stop auto-detecting glance API versions

This commit switches the image api tests from auto detecting which
api versions are available to having them explicitly set in the config
file. This is to make it explicit which tests are expected to be run
instead of assuming that everything is expected to work.

Partially Implements: blueprint config-cleanup

Change-Id: Ie958a7fb03ff502c5ea1783eaae9debb442c34ea
Merge "Stop auto-detecting glance API versions"