[#1792] Fix issue on FTS' where clause on specific fields

We were adding the value to the where_values with no need. We ended up with
more where_values than "%s" used in the where string, which could lead to
problems.

ckanext/datastore/plugin.py

@@ -409,8 +409,7 @@ def _where(self, data_dict, fields_types):
                     if field not in fields_types:
                         continue
                     query_field = self._ts_query_alias(field)
-                    clause_str = u'"{0}" @@ {1}'.format(field, query_field)
-                    clause = (clause_str, value)
+                    clause = (u'"{0}" @@ {1}'.format(field, query_field),)
                     clauses.append(clause)
 
         return clauses