Duplicating a level duplicates any Child Actor components of Blueprint Actors in the original level

Duplicating a level duplicates any Child Actor components of Blueprint Actors in the original level.

Reproduced in 4.8.3 binary and Main (//depot/UE4/Promotable-CL-2635815)

1. Open any project
2. Create a new Actor Blueprint
3. Create a second new Actor Blueprint
4. Add a Child Actor component
5. Set the Child Actor Class to the first new Actor Blueprint
6. Place the second Blueprint in the level
7. Duplicate the level

Result:
The Blueprint in the duplicated level has two Child Actor components

Expected:
The Blueprint in the duplicated level has one Child Actor component

ChildActors wrong duplicated when Duplicating Level