Entity linking not works properly

[mcolacino]

The symptom is a missing relation between a given entity and a given post once the disambiguation process is performed and the current post is saved

The bug happens when:

1. A given internal entity is not returned by the analysis, while is returned its dbpedia sameAs;
2. The user try to associate again the dbpedia version;
3. The internal entity uri cannot be inferred from the current entity label (ea: Yen giapponese vs http://data.wordlift.it/wl023/entity/japanese_yen)

The issue can be reproduced on 3.5 branch release.