Overridden mesh values are lost when upgrading from 5.5.0/5.5.1 to 5.5.2 on blueprint skeletal mesh components

This issue is caused by the backout in 38341618.  The original code that went into 5.0 affects serialization by changing the UCS modified properties.  When upgrading, the override is lost because the overriden property isn't getting serialized, as it's marked as UCS modified, and the code in SkeletalMeshComponentInstance data is no longer present in 5.5.2 to correct it.

1. Create a project in 5.5.1
2. Create an actor blueprint and add a skeletal mesh component
3. Drop the bp into the level viewport and change the Skeletal Mesh Asset property
4. Save the project and close
5. Open the project in 5.5.2
6. Note how the mesh displayed on the actor in the viewport has changed back to the default from the bp