Fix common path in _ ls_tree

[lhoestq]

The common path can be one of the directories to refresh.

This was causing a bug where the common path was the parent directory instead, and therefore glob would wrongly return content from the parent directory depending on the cache content

now this code returns the correct files

import fsspec
from huggingface_hub import HfFileSystem

fs: HfFileSystem
path = "hf://datasets/severo/bug-hfh-lfs/data/*"

fs = fsspec.get_fs_token_paths(path)[0]
print(fs.glob(path, detail=True))

print("=" * 100)

fs = fsspec.get_fs_token_paths(path)[0]
print(fs.glob(path, detail=True))

this bug was introduced in #1809

[mariosasko]

Thanks, LGTM!