Forward gunicorn reload parameter to uvicorn worker

[Kludex]

Basically a copy/paste from benoitc/gunicorn#2339 (comment) made by @jvasi

This solution pops up the following on reload:

[INFO] Error while closing socket [Errno 9] Bad file descriptor

Notes:

• I haven't investigated the issue above.
• I'm not sure if I want this to be merged, as it can be extended the way it was in the mentioned comment.

[Kludex]

This is not a satisfatible solution considering the reload system gunicorn uses. They make use of SIGHUP on the reload, and we should leverage that here.

[Kludex]

SIGHUP is not available on Windows, but gunicorn doesn't run on Windows anyway.