[IMP] res.users: remove special case for sudo() in read_group

Neither the super-user nor the sudo() mode should need
to use read_group() on any of the private user fields.
So we can simplify the code and remove this special case.

The same is not true for read(), though.

openerp/addons/base/res/res_users.py

@@ -312,10 +312,9 @@ class Users(models.Model):
 
     @api.model
     def read_group(self, domain, fields, groupby, offset=0, limit=None, orderby=False, lazy=True):
-        if self._uid != SUPERUSER_ID:
-            groupby_fields = set([groupby] if isinstance(groupby, basestring) else groupby)
-            if groupby_fields.intersection(USER_PRIVATE_FIELDS):
-                raise AccessError(_("Invalid 'group by' parameter"))
+        groupby_fields = set([groupby] if isinstance(groupby, basestring) else groupby)
+        if groupby_fields.intersection(USER_PRIVATE_FIELDS):
+            raise AccessError(_("Invalid 'group by' parameter"))
         return super(Users, self).read_group(domain, fields, groupby, offset=offset, limit=limit, orderby=orderby, lazy=lazy)
 
     @api.model