Realtime lights set to "Not Important" in Render Mode are not computed correctly in Shadowmask/Distance Shadowmask mode.

Steps for reproduction:
1) Download the project "VertexLightingBug.zip" and open the scene "Bug"
2) Generate the lighting in "Subtractive" mode
3) Observe that realtime point light contribute lighting to dynamic object (i.e. Sphere)
4) Change the light mode to "Shadowmask"
5) Observe that realtime point light does not contribute lighting to dynamic object

Notes:
- Lights that have their Render Mode set to Not Important are always per-vertex or SH. Vertex/SH light should be handled in shadowmask/distance shadowmask mode (i.e. occlusion should be computed on the CPU)
- In the reproduction scene, there is one mixed directional light, one realtime point light and there no light probes.
- On the image attached below, plane is light map static, sphere is dynamic
- It works correctly in deferred rendering path, but works incorrectly in forward rendering path.
- Not a regression, realtime lights set to “Not Important” never worked since the introduction of light modes