Quiet a server that's no longer in the cluster

If a server leaves a configuration it may not actually get the log entry replicated that removes it, so it'll try to start elections. The rest of the cluster will ignore it, but if we give it feedback to shut up it will be less of a noisy process.

The issue names no files, tests, or entry points. Start by locating the election behavior for a server that has left the configuration, then determine how the remaining cluster can signal that server to stop campaigning; done means the removed server no longer starts noisy elections.

Written by the indexing model from the issue text.