Add testcases for images

Adds tests for those GET API functions that accept params

Image_list glance API

Partial-Bug: #1086590

Change-Id: I9e2c5df63b066dd79ad8f5467b40bf3d6e252e98
moving to global lazy loaded config

one of the problems we've got with tempest is the fact that config
loading is tied into the class hierarchy. However there is no
reason why it should be. If we instead create a config proxy
object we can lazy load the actual config when we are executing,
and not do it at import time.

This could use future iteration, but it does a huge job in
removing config from the object inheritance tree which massively
simplifies our ability to use config variables throughout the code.

Change-Id: I9b1bbfe231c85c01938bd68be4e5974bd24130d6
Merge "Add testcases for images"