Stop gitlab-http-router before updating

What does this merge request do and why?

This MR attempts to fix one of the causes for #2159 by stopping gitlab-http-router before updating it.

If the wrangler.toml is updated, Wrangler will start new workerd processes but if the configuration is invalid, especially around ports, it will crash and be restarted by runit. Wrangler doesn’t clean up one of the workerd processes, so it lingers around.

Note that is is not a complete fix because an invalid configuration for other reasons could still cause this problem.

How to set up and validate locally

1. Run gdk start gitlab-http-router
2. Run make gitlab-http-router-update
3. Run gdk status gitlab-http-router
4. See that the router is not running

Impacted categories

The following categories relate to this merge request:

• gdk-reliability - e.g. When a GDK action fails to complete.
• gdk-usability - e.g. Improvements or suggestions around how the GDK functions.
• gdk-performance - e.g. When a GDK action is slow or times out.

Merge request checklist

• This change is backward compatible. If not, please include steps to communicate to our users.
• Tests added for new functionality. If not, please raise an issue to follow-up.
• Documentation added/updated, if needed.
• Announcement added, if change is notable.
• gdk doctor test added, if needed. (See Add workerd diagnostic (!3932 - merged))
• Add the ~highlight label if this MR should be included in the CHANGELOG.md.