Decentralized learning fails with error

[JulienVig]

Training collaboratively for decentralized learning tasks fails with error:

Uncaught Error: Connection failed.
    _onConnectionStateChange simplepeer.min.js:6
    onconnectionstatechange simplepeer.min.js:6
    _onConnectionStateChange simplepeer.min.js:6
    onconnectionstatechange simplepeer.min.js:6
    dispatchEvent PeerConnection.sys.mjs:836
    dispatchEvent PeerConnection.sys.mjs:1822
    onStateChange PeerConnection.sys.mjs:1952

The error arises right after clicking Train collaboratively, before any training update happens.

To Reproduce

1. Start a server and two web-clients
2. Connect some data for a decentralized task (I used the lus_covid tasks and modified it to be decentralized)
3. Clicking train collaboratively for both web-clients.
4. Check the browser console logs where the error should appear