csplit-io-err.sh: seq 100 | csplit - 1 should fail if xx01 is symlink to /dev/full

```
$ uu-ln -sf /dev/full xx01
$ seq 100 | uu-csplit - 1
0
292
$ file xx01
xx01: symbolic link to /dev/full
$ seq 100 | gnu-csplit - 1
0
csplit: xx01: No space left on device
$ file xx01
xx01: cannot open `xx01' (No such file or directory)
```