UObject Rename always changes object name

In general, Object names should try to be reused where ever possible. This can help with name clashes and flexibility in finding / referencing objects by name.

The implication for UObject::Rename was that when no name was passed in, it would try to keep the Object's current name, and only change it if necessary.

1. Create an Actor with some UObject property.
2. In the constructor, create the object and give it a unique name.
3. Create a second Actor with some UObject property.
4. In the constructor, create the object and give it a unique name (different from the first).
5. Use UObject::Rename to re-parent the second UObject to the first Actor, passing in nullptr for the name.

Expected: The second UObject will be re-parented to the first Actor, and keep its current unique name.

Actual: The second UObject will be re-parented to the first Actor, but will be given a new name.