mv: two self-referential symlinks cause very long runtime

coreutils 0.11.0 (multi-call binary)
commit 4a41d0ba51f (latest)

Commit 175cfdc (mv: don't put a symlink in its target's hardlink group) causes mv to burn hours of cpu cycles:

```
mkdir -p /tmp/poc/d /tmp/dest
ln -s . /tmp/poc/d/l1
ln -s . /tmp/poc/d/l2
mv /tmp/poc/d /tmp/dest/
```

