Volumetric Lightmaps Persist When Opening Different Level

When moving between levels with built lighting volumetric light maps persists between levels.

Workaround: Load the same level twice.

Found in 4.24.2 CL#11100242
Reproduced in 4.26 Main CL#11574810

1. Create a new level (RedMap) place multiple primitives and point lights in a scene. Make the points lights emit red.
2. Duplicate RedMap and name it BlueMap.
3. Change all the point lights in a scene to blue.
4. Show the volumetric light map (Show->Visualize->Volumetric Lightmap).
5. Load RedMap and show the volumetric light map from the Content Browser.
6. Load BlueMap and show the volumetric light map from the Content Browser.

Result: The light map for the last open map persists.

Expected: The light map for the current level is loaded.