Undecryptable messages after a server fails to federate.

### Steps to reproduce

1. I stood up a new server
2. I forgot to include the letsencrypt intermediary in its cert file, so it couldn't federate
3. I fixed this and then invited it to a room from matrix.org
4. however, matrix.org had been blacklisted as a destination (for 10 mins) thanks to federation not working
5. surprisingly, the invite came through and i could answer it
6. but messages sent to matrix.org were "** Unable to decrypt: The sender was unable to establish a secure channel. **" on the receiving EWs - it looks like the messages arrived transitively via another non-blacklisted server.
7. Once the 10 minutes elapsed however, the history is still broken - and new messages in both directions are still broken too.

### Outcome

Encryption should recover once federation recovers.

Instead, it looks like

a) my synapse didn't mark matrix.org as unblacklisted once we saw traffic from it
b) my test EW didn't retry setting up Olm correctly (or the megolm wasn't retried too)
c) my normal EW also wasn't able to set through.

### Operating system

macOS 12.1 on M1

### Application version

Nightly

### How did you install the app?

_No response_

### Homeserver

_No response_

### Will you send logs?

Yes