Ensure that layers are not excluded from manifests based on previous pushes.
Continue skipping pushes on layers which were pushed by a previous tag.
Update push multiple tag tests.
Ensure that each tag pushed exists on the registry and is pullable.
Add output comparison on multiple tag push check.
fixes#15536
Signed-off-by: Derek McGowan <derek@mcgstyle.net> (github: dmcgowan)