fix acme middleware passing handled requests to parent middlewares

What does this MR do?

if ServeFileHTTP returns true the request has been handled and something has been served, it shouldn't be passed to the other middlewares.

TODO

• I added the Changelog trailer (e.g. Changelog: added) to the commits that need to be included in the changelog
• I added unit tests or they are not required
• I added acceptance tests or they are not required
• I added documentation (or it's not required)
• I followed code review guidelines
• I followed Go Style guidelines