Add trailing slash on status route for coherence with others

[maudetes]

Follows https://github.com/datagouv/hydra/pull/119

We would actually like to have a redirection instead of a 404 on trailing slash or not, but for now let's keep it coherent with other routes at least.

[bolinocroustibat]

Thanks for spotting. The trailing slash management in aiohttp routes is really not ideal, there should be a way for both to work. For now thanks for the fix, LGTM!