Cycles; Correction to previous debug print to survive prints from multiple threads
Cycles; Correction to previous debug print to survive prints from multiple threads

This commit basically makes it so statistics print from different BVH trees are not
being interleaved with each other. Glog ensures this when debug print is done as a
single put to stream operator.

tangent-opensource/coreBlackbird,tangent-opensource/coreBlackbird,tangent-opensource/coreBlackbird