message: fix(client): change connection errors to debug log level
  Closes
diff: @@ -198,7 +198,7 @@ where C: Connect,
  let pooled = pool.pooled(pool_key, tx);
  let conn = proto::Conn::<_, _, proto::ClientTransaction, _>::new(io, pooled.clone());
  let dispatch = proto::dispatch::Dispatcher::new(proto::dispatch::Client::new(rx), conn);
  - handle.spawn(dispatch.map_err(|err| error!("client connection error: {}", err)));
  + handle.spawn(dispatch.map_err(|err| debug!("client connection error: {}", err)));
  pooled
  })
  };
  