Scene actors in the hierarchy are re-ordered when the scene is reload

[adriengivry]

Description

Scene actors are reordered in the hierarchy after reloading a scene.

To Reproduce

Steps to reproduce the behavior:

1. Create a new scene
2. Add a sphere
3. Add a cube
4. Move sphere under the cube in the hierarchy by drag-and-dropping it into the hierarchy background
5. Hit play
6. Hit stop
7. Notice the sphere is back on top of the cube in the hierarchy

Expected behavior

Placement in the hierarchy should be preserved

Screenshots

Initial Setup	After Drag-Drop	After Play/Stop