@Override
    MessageFormatFlags getOperationFlag() {
      return MessageFormatFlags.BlobInfo;
    }
Return {@link MessageFormatFlags} to associate with cached first chunk.
For a cached metadata chunk, we just need to get blobInfo to validate it.
We don't have to fetch the entire metadata chunk again.
@return {@link MessageFormatFlags#BlobInfo}
ambry-router/src/main/java/com/github/ambry/router/GetBlobOperation.java