Add agent server (kas) to dsop-scripts

The agent server is a component you install together with GitLab. It is required to manage the GitLab agent for Kubernetes.

This MR adds the agent server container (gitlab-kas) to the dsop scripts so it will be included when a release is pushed to repo1.

• Updates the release helper, so each releaseImage call can specify it's base image and overwrite the base image tag (which defaults to the gitlab version, but we want to be the UBI tag if the image is based on a ubi base image)
• Hacks in support for kas to build using the ubi8-minimal image when we are building locally for testing using the build scripts
• Adds the kas release