message: storage: make blob_index/set_blob_index not v5 specific
  Make BlobInfo::blob_index/set_blob_index() as common instead of v5
  specific. It will be used by BlobDevice later.
diff: @@ -171,15 +171,18 @@ impl BlobInfo {
  /// Get the blob index in Rafs v5 metadata's blob array.
  pub fn blob_index(&self) -> u32 {
  - assert!(self.is_v5());
  self.blob_index
  }
  /// Set the blob index in Rafs v5 metadata's blob array.
  pub fn set_blob_index(&mut self, blob_index: u32) {
  - assert!(self.is_v5());
  self.blob_index = blob_index;
  }
  +
  + /// Check whether the Rafs v5 metadata blob has extended blob table.
  + pub fn with_v5_extended_blob_table(&self) -> bool {
  + self.blob_version == BlobVersion::V5 && self.chunk_count != 0
  + }
  }
  bitflags! {
  