Precomputed lighting is not saved when using Save As or Duplicate for levels

Lighting is invalidated with levels that have been duplicated or Saved As. The maps that are created are immediately marked dirty and need to be resaved vs how they were in 4.12.5 where they wouldn't be marked dirty.

This is a regression from previous behavior in 4.12 release.

Builds tested with:
Working: 4.12.5 CL-3039270
Broken: 4.13.0 CL-3106830
Broken: 4.13.1 CL-3142249
Broken: 4.14 Dev-Framework CL-3145267

1. Open UE4
2. Create a new default level
3. Add some meshes and build lighting
4. Save the level and give a name
5. After saving, Go to File > Save As and save the level again as a different name

Regression: Yes

Results: Lighting is invalidated in the copied or saved as level

Expected: Lighting should not be invalidated

4.13.1 Saving a level using "save as" breaks lightmaps, lighting needs to be rebuilt