More useful to log the errno value when setxattr() fails?

Hi there,

According to the documentation of `setxattr()`:

```
On success, 0 is returned.  On failure, -1 is returned and the global variable errno is set as follows...
```

Therefore logging the value of `result` at this point is redundant and not useful for debugging purposes. Surely better to log `errno` so that the user can find the source of the problem in `errno.h`?

Thanks!