fix flags setting bug (#91)

Fixing a bug in #90, didn't set the
flag correctly so cache was not disabled, so xet cp download didn't get
the maximum speedup.

Confirmed after this fix, downloading 137.9 GB data reaching 4.5 Gbps
(bottlenecked by disk) in us-west, matching the previously [benchmarked
results](https://www.notion.so/xethub/xet-cp-download-benchmark-655e0d5fa4ea45e5817fee6f99ad8b06).
```
(.env) ubuntu@ip-10-0-27-153:~/data/pyxet/python/pyxet$ time xet cp -r -p 3 xet://XetHub/Llama2/main/models/llama-2-70b-chat ~/data
...
real    4m6.189s
user    2m2.321s 
sys     4m58.232s

```

python/pyxet/pyxet/file_system.py

@@ -1,7 +1,7 @@
 import json
 import sys
 from urllib.parse import urlparse
-from enum import Enum
+from enum import IntEnum
 
 import fsspec
 import os
@@ -32,7 +32,7 @@ def open(file_url, mode="rb", **kwargs):
     fs = XetFS()
     return fs._open(file_url, mode=mode, **kwargs)
 
-class XetFSOpenFlags(Enum):
+class XetFSOpenFlags(IntEnum):
     FILE_FLAG_NO_BUFFERING = 0x20000000
 
 class XetFS(fsspec.spec.AbstractFileSystem):

python/pyxet/pyxet/util.py

@@ -77,7 +77,7 @@ def _single_file_copy(src_fs, src_path, dest_fs, dest_path,
 
             # Fasttrack for downloading a file to local
             if src_fs.protocol == "xet" and dest_fs.protocol == "file":
-                with src_fs.open(src_path, "rb", {"flags": XetFSOpenFlags.FILE_FLAG_NO_BUFFERING}) as source_file:
+                with src_fs.open(src_path, "rb", flags=XetFSOpenFlags.FILE_FLAG_NO_BUFFERING) as source_file:
                     source_file.get(dest_path)
             else:
                 with src_fs.open(src_path, "rb") as source_file: