Better handle Syncthing's certificate renewal

[Martchus]

Syncthing sometimes re-generates its HTTPs certificate:

[INFO]    Loading HTTPS certificate: certificate will soon expire
[INFO]    Creating new HTTPS certificate
[INFO]    TCP listener ([::]:22000) starting

At this point this leads to tons of TLS errors on startup. The TLS error goes away by explicitly re-connecting from the settings. There's room for improvement:

• Suppress TLS errors in the time frame these log messages occur in Syncthing's log. This will at least help if Syncthing is started via the built-in launcher.
• Ensure the certificate is re-loaded automatically after running into an error so one doesn't need to re-connect from the settings manually.

[Martchus]

This should be fixed by 07ff8a5 where I now decided to simply reload the certificate before emitting any errors (so the first point is not necessary). Not sure whether it works because I only tested this in a rather artificial way.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[Martchus]

I haven't seen the error anymore so I suppose this worked.