Fix for intra-cmp backref problems.  ValueFactory.create works as a setValue,
but we only want to do that if the backref is the "expected" one, not for a
random other attribute (same or different component).  Those are copies.

So we need to pass the expected value down from MapValue.add.

@rev dval@
@bug W-2336292@
Merging origin/fabbott/master-pending/backref-attrs into master