When building in the Open Build Service (OBS) there is no way
to create outgoing connections from the build workers. To allow
the <containers> section to fetch containers from the SUSE
registry we need to apply an OCI URI translation into a local
path. The actual OCI container image is expected to be provided
by the obs backend on the worker. Along with this commit also an
integration test named test-image-disk-containers is provided.
This Fixes jira#OBS-351
