message: [state sync] use synced_state as known version
  Closes:
  Approved by: dmitri-perelman
diff: @@ -89,7 +89,10 @@ impl ExecutorProxyTrait for ExecutorProxy {
  let client = Arc::clone(&self.storage_read_client);
  async move {
  let resp = client.get_startup_info_async().await?;
  - resp.map(|r| r.ledger_info.version())
  + resp.map(|r| {
  + r.synced_tree_state
  + .map_or(r.ledger_info.version(), |s| s.version)
  + })
  .ok_or_else(|| format_err!("failed to fetch startup info"))
  }
  .boxed()
  