Fix 'add' call when 'update' on OrderedSet
Fix 'add' call when 'update' on OrderedSet

OrderedSet performs its 'update' method by calling the 'add' one. This
introduces extra call to 'add' so extra notifications. This commit
simply check in the 'add' method if the call comes from an orderedset
or not.

aranega/pyecore,pyecore/pyecore