GitLab Runner service uninstalled when turning off vm

Overview

During production#3872 (closed) we have to run graceful shutdown. Where we run sudo /root/runner_upgrade.sh stop_and_poweroff which stops the service. After the VM is booted we have to run sudo /root/runner_upgrade.sh update which runs chef-client but this fails with the following :

gitlab-runner.service doesn't exist

To fix this we would need to run apt-get install --reinstall gitlab-runner=13.9.0-rc2

Root cause

This comes from gitlab-runner uninstall that is part of the stop CLI. So when the VM reboots gitlab-runner doesn't automatically start.

Proposal

Change https://gitlab.com/gitlab-cookbooks/cookbook-wrapper-gitlab-runner/-/blob/5e7acd6d8925f50e4909efb24b45993237b608fb/files/default/runner_upgrade.sh#L25-26 to be sudo systemctl disable gitlab-runner instead so the service is disabled by not uninstalled.

/cc @tmaczukin @igorwwwwwwwwwwwwwwwwwwww