WebStyle: more accurate "Restricted" flag display

• Rely on search_engine.get_restricted_collections_for_recid(..) and search_engine.is_record_in_any_collection(..) in order to test if restricted flag should be displayed or not, instead of search_engine.record_public_p(..). It avoids displaying the flag when the record belong to a collection not directly searchable from the home collection. It allows to display an alternative flag when the record has not been fully integrated (not linked to any collection). It also display the restricted flag on record belonging to both a restricted collection and a public collection searchable from the home tree. (addresses #867)

• Added regression test for record belonging to both a public and a restricted collection.

Reviewed-by: Tibor Simko <tibor.simko@cern.ch>