Servers refuse to replicate

It is possible for a server to get itself in a state where it will never accept replication logs from other servers until it is restarted.

I encountered this while debugging but I believe it must be possible to get in this state during normal execution.

It seems that there is a case where a server starts a replication transaction (sets ReplicationServerContextHandler#replicaInTransaction) but fails to notice that it has ended (perhaps due to a message timeout?)