Make the image name configurable
Make the image name configurable

Remove the hardcoded "user" for the image name.
Remove the hardcoded container type and format.

Change-Id: Id17f3ef8f5b73b4805b29fd1a8d2f23ac7ed0770

rdo-management/tripleo-image-elements,openstack/tripleo-image-elements,radez/tripleo-image-elements,openstack/tripleo-image-elements,rdo-management/tripleo-image-elements,radez/tripleo-image-elements