Fix GitLab CI issues
@zuka0828 reported an issue on cip-dev where the CI builds were no longer working:
$ /kas/docker-entrypoint
useradd: user 'builder' already exists
error: failed switching to "builder": operation not permitted
This issue was caused by an upgrade to the GitLab CI runners that we use.
This MR fixes this.
In addition a patch has been added to restrict the deploy stage to the main cip-core-buster branch only, so we don't end up replacing the official binaries with those from test/developer branches.