CSITs are failing regularly due to download rate limits that were
recently introduced on dockerhub. Modified the yaml files to download
all images from nexus3 instead of dockerhub.
Issue-ID: POLICY-2895
Change-Id: I3ce37a5fc65fa82ddf1124653019cb24ff73f9ee Signed-off-by: Jim Hahn <jrh3@att.com>