"Connection refused" in Mumble when hosting on Whonix

[JeremyRand]

Steps to reproduce

1. Install the onion-grater profile into Whonix-Gateway.
2. Run Wahay on Whonix-Workstation.
3. Host a meeting.
4. Join your own meeting.

Expected results

Mumble should connect.

Observed results

Mumble says Server connection failed: Connection refused.

Other notes

This is because the Tor daemon is receiving an IP of 0.0.0.0 for the ADD_ONION event, thus it's forwarding the incoming onion service connections to the wrong IP.