Small reproduction steps:
1) Download "LightProbeSample2017" below
2) Ensure that scenes are loaded additively and scene "Test" is master scene
3) Generate the lighting
4) Enter play mode
5) Observe the loading time difference in 2017.1 and 2017.2. There is a performance regression with light probe loading

Notes:
- Light probes only exist in first loaded scene (Master Scene)
- Editor.log is attached below too
- Apparently regressed in 2017.2 after the introduction of time slicing/async load feature in Enlighten

Fix will be backported to 2018.2