Fix step: Restart the Runner

What does this Merge Request do?

This MR changes updates the gitlab-runner restart step as it stops and then starts the GitLab Runner service.

Instead, what we need is to stop and run again the runner that we registered during the setup.

Merge Request checklist

• [-] Tests added for new functionality. If not, please raise Issue to follow-up.
• [-] This change is backward compatible. If not, please include steps to communicate to our users.
• Documentation added/updated, if needed.
• [-] gdk doctor test added, if needed.