message: 1.fix export snapshot
diff: @@ -1153,6 +1153,8 @@ fn export_column(
  /// block_info num block.header.hash
  /// txn_accumulator num accumulator_root_hash
  /// state num state_root_hash
  +/// state_node_prev num state_root_hash
  +
  pub fn export_snapshot(
  from_dir: PathBuf,
  output: PathBuf,
  @@ -1222,7 +1224,7 @@ pub fn export_snapshot(
  let num = str_list[1].parse::<u64>()?;
  old_snapshot_nums.insert(column, num);
  }
  - if old_snapshot_nums.len() != 5 {
  + if old_snapshot_nums.len() != 6 {
  println!("increment export snapshot manifest.cvs error");
  std::process::exit(1);
  }
  @@ -1337,27 +1339,27 @@ pub fn export_snapshot(
  }
  manifest_list.push((
  - STATE_NODE_PREFIX_NAME_PREV,
  - nums_prev.load(Ordering::Relaxed),
  - state_root_prev,
  + STATE_NODE_PREFIX_NAME,
  + nums.load(Ordering::Relaxed),
  + state_root,
  ));
  println!(
  "{} nums {}",
  - STATE_NODE_PREFIX_NAME_PREV,
  - nums_prev.load(Ordering::Relaxed)
  + STATE_NODE_PREFIX_NAME,
  + nums.load(Ordering::Relaxed)
  );
  manifest_list.push((
  - STATE_NODE_PREFIX_NAME,
  - nums.load(Ordering::Relaxed),
  - state_root,
  + STATE_NODE_PREFIX_NAME_PREV,
  + nums_prev.load(Ordering::Relaxed),
  + state_root_prev,
  ));
  println!(
  "{} nums {}",
  - STATE_NODE_PREFIX_NAME,
  - nums.load(Ordering::Relaxed)
  + STATE_NODE_PREFIX_NAME_PREV,
  + nums_prev.load(Ordering::Relaxed)
  );
  // save manifest
  @@ -1654,7 +1656,7 @@ pub fn apply_snapshot(
  if index % BATCH_SIZE == 0 {
  bar.set_message(format!(
  "import {} index {}",
  - STATE_NODE_PREFIX_NAME,
  + STATE_NODE_PREFIX_NAME_PREV,
  index / BATCH_SIZE
  ));
  bar.inc(1);
  