message: builder: use chunk v1 for native directory build
  Keep backward compatibility for old nydusd, otherwise the old nydusd
  will throw a panic like:
  ```
  ERROR [error/src/error.rs:21] Error:
  "blob metadata size is too big!"
  at storage/src/meta/mod.rs:344
  note: enable `RUST_BACKTRACE=1` env to display a backtrace
  ```
diff: @@ -699,12 +699,7 @@ impl Command {
  };
  let mut builder: Box<dyn Builder> = match conversion_type {
  - ConversionType::DirectoryToRafs => {
  - if version.is_v6() {
  - build_ctx.blob_meta_features |= BLOB_META_FEATURE_CHUNK_INFO_V2;
  - }
  - Box::new(DirectoryBuilder::new())
  - }
  + ConversionType::DirectoryToRafs => Box::new(DirectoryBuilder::new()),
  ConversionType::DirectoryToStargz => unimplemented!(),
  ConversionType::DirectoryToTargz => unimplemented!(),
  ConversionType::EStargzToRafs => Box::new(TarballBuilder::new(conversion_type)),
  