Build a OSG node for OctreeNode no matter if it is active or not.
Build a OSG node for OctreeNode no matter if it is active or not.

A OctreeNode may be activated later even if it is inactive in the
beginning.

Also, revise the implementation of setOctree() since its signature has
changed.

simquest/opensurgsim,simquest/opensurgsim,simquest/opensurgsim,simquest/opensurgsim