Skip duplicate call signatures
Skip duplicate call signatures

I am seeing `p` twice for os.path.dirname, which seems to come from
Lib/posixpath.py and Lib/ntpath.py, as can be seen with `os.path.join`,
where I still see two with this patch:

```
            (path, *paths)
import os   (a, *p)
os.path.join()
```

davidhalter/jedi-vim