Fix bug in reimplementation of neighbor_lists.
Fix bug in reimplementation of neighbor_lists.

mit-crpg/openmc,liangjg/openmc,samuelshaner/openmc,johnnyliu27/openmc,amandalund/openmc,samuelshaner/openmc,amandalund/openmc,johnnyliu27/openmc,walshjon/openmc,paulromano/openmc,mjlong/openmc,liangjg/openmc,shikhar413/openmc,amandalund/openmc,mit-crpg/openmc,smharper/openmc,smharper/openmc,samuelshaner/openmc,johnnyliu27/openmc,bhermanmit/openmc,liangjg/openmc,samuelshaner/openmc,smharper/openmc,shikhar413/openmc,wbinventor/openmc,paulromano/openmc,wbinventor/openmc,wbinventor/openmc,walshjon/openmc,mjlong/openmc,walshjon/openmc,paulromano/openmc,bhermanmit/openmc,kellyrowland/openmc,shikhar413/openmc,amandalund/openmc,paulromano/openmc,smharper/openmc,mit-crpg/openmc,mit-crpg/openmc,wbinventor/openmc,johnnyliu27/openmc,shikhar413/openmc,walshjon/openmc,liangjg/openmc,kellyrowland/openmc