https://bugs.eclipse.org/bugs/show_bug.cgi?id=271321
NPE when running VerifyAggregateCollectionObjectsDeletedFromCacheTest
introduced by fix https://bugs.eclipse.org/bugs/show_bug.cgi?id=221389
Serialization for cache co-ordination does not support having
AggregateCollection elements in the removedList of the
AggregateCollectionChangeRecord.
Solution is to clear these lists during "prepareForSerialization".
Any feedback is welcomed.
--Gordon