Simple optimizations to Universe._determine_paths
Simple optimizations to Universe._determine_paths

paulromano/openmc,amandalund/openmc,paulromano/openmc,johnnyliu27/openmc,mit-crpg/openmc,smharper/openmc,liangjg/openmc,mit-crpg/openmc,walshjon/openmc,wbinventor/openmc,smharper/openmc,walshjon/openmc,wbinventor/openmc,walshjon/openmc,johnnyliu27/openmc,liangjg/openmc,wbinventor/openmc,shikhar413/openmc,johnnyliu27/openmc,smharper/openmc,amandalund/openmc,mit-crpg/openmc,amandalund/openmc,smharper/openmc,amandalund/openmc,liangjg/openmc,paulromano/openmc,wbinventor/openmc,liangjg/openmc,shikhar413/openmc,shikhar413/openmc,walshjon/openmc,paulromano/openmc,mit-crpg/openmc,johnnyliu27/openmc,shikhar413/openmc