dd: should return 1 when stderr is redirected to /dev/full but returns 101

GNU dd v9.4.113-c01ee:
```
$ : | dd 2> /dev/full; echo $?
1
```

uutils dd:
```sh
$ : | ./target/debug/dd 2> /dev/full; echo $?
101
```

This test case appears in GNU test suite file `tests/dd/stderr.sh`.
