[tor-relays] planned downtime

[Damian Johnson]

> If someone chose to use, or only could use, his relays.
> Or to give a reason other than being raided or broke :)

A heads up would make sense if he was providing bridges, since that
would impact reachability for his users. However, if it's a normal
relay then there's really no point in sending a downtime notice. Paul
is right that we see hundreds of relays appear or disappear each day
and, besides a few particularly huge ones, the downtime probably
wouldn't be noticed.