message: nydus-test: don't test nydus-image for localfs backend
  nydus-image can't move directly blobs to a specified dir anymore.
  So adapt it.
diff: @@ -216,10 +216,11 @@ def test_prefetch_with_cache(
  rafs.umount()
  -@pytest.mark.parametrize("compressor", [Compressor.NONE, Compressor.LZ4_BLOCK])
  -@pytest.mark.parametrize("backend", [Backend.BACKEND_PROXY, Backend.LOCALFS])
  -@pytest.mark.parametrize("amplified_size", [Size(3, Unit.MB).B, Size(3, Unit.KB).B])
  -def test_large_file(nydus_anchor, compressor, backend, amplified_size):
  +@pytest.mark.parametrize(
  + "compressor", [Compressor.NONE, Compressor.LZ4_BLOCK, Compressor.ZSTD]
  +)
  +@pytest.mark.parametrize("amplified_size", [Size(3, Unit.MB).B, Size(32, Unit.KB).B])
  +def test_large_file(nydus_anchor, compressor, amplified_size):
  _tmp_dir = tempfile.TemporaryDirectory(dir=nydus_anchor.workspace)
  large_file_dir = _tmp_dir.name
  @@ -231,13 +232,13 @@ def test_large_file(nydus_anchor, compressor, backend, amplified_size):
  dist.put_multiple_files(10, Size(4, Unit.MB))
  image = RafsImage(nydus_anchor, large_file_dir, "bs_large", "blob_large")
  - image.set_backend(backend).create_image(compressor=compressor)
  + image.set_backend(Backend.BACKEND_PROXY).create_image(compressor=compressor)
  rafs_conf = (
  RafsConf(nydus_anchor, image)
  .enable_rafs_blobcache()
  .amplify_io(amplified_size)
  - .set_rafs_backend(backend, image=image)
  + .set_rafs_backend(Backend.BACKEND_PROXY, image=image)
  )
  rafs = NydusDaemon(nydus_anchor, image, rafs_conf)
  