Update Starter Kits to pass vulnerability scanning

The build pipelines can optionally scan the image for vulnerabilities before deploying. Many (all?) of our Starter Kits do not pass. Let's see if we can update them to pass vulnerability scanning.

For example, Tekton task [ibm-img-scan](https://github.com/IBM/ibm-garage-tekton-tasks/blob/main/tasks/9-img-scan.yaml) does vulnerability scanning, using different scanners depending on the Toolkit's configuration.

THIS IS NOT A REQUIREMENT FOR IMAGE CERTIFICATION, but is a nice-to-have. If getting this working becomes too difficult, it may not be a high enough priority to fix. But if the Toolkit can't make images for Hello World apps that pass vulnerability scanning, what chance to users with real applications have?

This issue and/or issue #779: Update Dockerfiles to build from latest UBIs may be a duplicate of issue #772: Provide clean versions of the base images from RedHat that will pass Vulnerability Advisor scan.