lots of wasted Volumetric lightmap samples

Expectations: The samples should only surround the lightmass importance volumes. 

Imagine if we build a 8K*8K map with lightmap importance volume at the corners of the map, even using stream levels(because VLM can not be streamed now) the build data only for VLM would be around 10M*8*8*8=5120M！which even only contain the lowest level of VLM

This issue is similar to this one other than using two small Lightmap importance volume instead of a big one

https://forums.unrealengine.com/development-discussion/rendering/1394082-volumetric-lightmap-samples-bug-reproduce-able

• New a empty level
• Put  two Lightmap Importance volume with default size(200*200*200) into the level
• Place one at world location of (0.0.0), the other at world location of (100000.0.0)
• Built lighting

There's a huge mount of samples filled in to a huge cubic bounds that encompasses the two lightmass importance volumes

Check the output log see LogVolumetricLightmapImport:      Indirection Texture 128x128x128 = 8.0Mb

Save the map, the build data is about 10M

Show those samples in viewport like this

  [Link Removed]