Update images config and client

*Updated images config file
-Added primary_image_default_user property
*Updated images client
-Replaced 'type_' with 'type' to fix broken tests
*Updated images types
-Added 'snapshot' to ImageType class

Change-Id: I0b2d712bed767d3173a561d59e6e8d7fb7932ef5
Merge "Update images config and client"