Utah directory being written to blocks parent directory listing.

I have mounted utahfs in my home directory, under `$HOME/Utah` to experiment with. When copying a large file in, the parent directory becomes blocked from listing. Attempting to `Ctrl+C` ls does work, but takes a long time.

Steps to reproduce
```bash
~$ # Terminal 1
~$ utahfs-client -conf ~/utahfs.yaml -mnt ~/Utah
~$ cp largefile Utah/largefile
```

```bash
~$ # Terminal 2
~$ ls

```

Eventually the operation can be killed, the following log is printed:

```
2020/06/23 12:00:02 filesystem.go:661: context canceled
fuse: 2020/06/23 12:00:02 connection.go:486: *fuseops.GetInodeAttributesOp error: app: transaction not active
```