[eclipselink-dev] checked in fix for 391833 - Duplicate insert on lazy s

[Christopher Delahunt <christopher.delahunt@xxxxxxxxxx>]

Fix for 391833 - Duplicate insert on lazy set with attribute change tracking

Simple fix to IndirectSet to check the value returned from delegate.Add 
before firing a change event.
Test testAddDuplicateToUninstantiatedSet  added to 
jpa.inheritance.EntityManagerJUnitTestCase

checked into main (2.5)
Reviewed by David Minsky