message: Nydusify: fix manifest parser for checker
  Parser parses manifest list by specified image reference,
  Prior to this patch, Parser would return immediately after
  parsing the OCI manifest, causing the checker to never find
  the Nydus manifest, resulting in this error:
  ```
  validate rule Manifest: invalid nydus image manifest
  ```
diff: @@ -221,14 +221,12 @@ func (parser *Parser) Parse(ctx context.Context) (*Parsed, error) {
  } else {
  ociDesc = &desc
  }
  - break
  }
  } else {
  // FIXME: Returning the first image without platform specified is subtle.
  // It might not violate Image spec.
  ociDesc = &desc
  logrus.Warn("Will cook a image without platform, %s", ociDesc.Digest)
  - break
  }
  }
  }
  