updated docker images

As a follow-up on cactus-buildenv!1 (merged)

This changes the CI to use the new buildenv images, and creates the following new images itself

• xdaq14-ts51:cc7 (latest build on master)
• xdaq14-ts51:cc7-2020-06-24 (build on master on 2020-06-24)
• xdaq14-ts51:gldirkx-updated-docker-images-cc7-2020-06-24 (build on feature branch on 2020-06-24)