Fix endless loops when directories symlinks to themselves

Some modules apparently have links that looks like this:

$ ls -l
total 0
lrwxrwxrwx 1 thhal thhal 1  9 maj  2014 lib -> .
lrwxrwxrwx 1 thhal thhal 1  9 maj  2014 manifests -> .

Geppetto handled that in a bad way by running into an endless
loop.