Delta applied twice when moving parent and grouped child actors

When some grouped actors are childed to another actor, and both the group and the parent are selected in the world outliner, movement delta is applied twice to the grouped children. Code for a potential fix is provided by licensee on UDN.

1. Create 3 actors, A, B & C
2. Attach B & C to A
3. Group B & C
4. Select A, B & C
5. Attempt to move them
6. Child actors apply movement delta twice