Only announce to new peers when polling storage

Problem: whenever a storage operation wakes us we announce the new
document to all the peers we are connected to. This was intended to
announce documents when loading, but it means we also announce every
time we save.

Solution: only announce to peers whom we do not currently have a
connection when polling storage.

src/repo.rs

@@ -1829,10 +1829,11 @@ impl Repo {
                                         &self.repo_id,
                                     );
                                     if info.state.should_sync() {
+                                        let remotes = self.remote_repos.keys().filter(|k| !info.peer_connections.contains_key(k));
                                         // Send a sync message to all other repos we are connected
                                         // with and with whom we should share this document
                                         Self::enqueue_share_decisions(
-                                            self.remote_repos.keys(),
+                                            remotes,
                                             &mut self.pending_share_decisions,
                                             &mut self.share_decisions_to_poll,
                                             self.share_policy.as_ref(),