message: nydus-test: give 64 chars string blob id to nydus-image
  Which enforces nydus-image blob id
diff: @@ -799,7 +799,7 @@ def test_build_image_param_blobid(
  """
  # More strict id check?
  nydus_image.set_backend(Backend.BACKEND_PROXY).set_param(
  - "blob-id", uuid.uuid4()
  + "blob-id", utils.random_string()
  ).create_image()
  rafs_conf.set_rafs_backend(Backend.BACKEND_PROXY)
  rafs = RafsMount(nydus_anchor, nydus_image, rafs_conf)
  