Config file for runner doesn't fit system install?

[gilou]

The conf file should probably be checked in /etc/gitlab-runner/config.toml rather than in the home to allow configuration in

gitlab-formula/gitlab/runner.sls

Line 43 in 191fe84

- unless: 'test -e /home/{{gitlab.runner.home}}/config.yml'

Also this is not idempotent as the register is not either... Maybe we can use gitlab-runner verify to check if the configured runner is already registered?