wrong git branch when running on leolivier gitlab runner

Job #1414296586 failed for e6d31c83: When running the jobs on @siweber gitlab runners, the command

svc_branch=$(cd ../.. && git submodule status stage7-addons/00-copy-generation-files/files/pier-services | awk '{print $3}' | sed -e 's&(remotes/origin/\(.*\))$&\1&')

in stage7 00-run.sh returns "HEAD" and everything works fine. When it runs on @leolivier gitlab runner, it returns something like "master-xx-xxx" instead and the job fails because we try check this branch out and it doesn't exist