Impossible recovery after asking recovery of a not running ZEO server

[Sylvain Viollon]

In the case you have a zeoraid connected to two zeo server.

1. You stop one of zeo server used to store data.
2. If you run the manage details command, you see that that zeo server is disconnected.
3. You run the manage recover command for that zeo server.
4. If you run the manage details command, you see that that zeo server is recovering: ???.
5. You start again that stopped zeo server.
6. If you run the manage details command, you see that the status is still recovering: ??? even after a while.
7. If you re-run the manage recover command, it just display None, and that doesn't change the status of the zeo server, it is still recovering: ???. Only a full restart of everything seems to fix the problem.