T2_CH_CERN site-local-config not accessible outside of CERN

The site-local-config.xml setup in the standalone image (https://gitlab.cern.ch/cms-cloud/cmssw-docker/-/blob/master/standalone/Dockerfile#L39-41) references T2_CH_CERN. This site is not accessible outside of CERN. We got around this using the prescription here. We stored a replacement site-local-config.xml in the repo because of all of the changes necessary. If these images are going to be used by people around the world, it would be nice if the configurations were setup to be accessible outside of CERN. I can create a PR to make this change if you'd like.