Fix error in bounding boxes for y- and z-planes.
Fix error in bounding boxes for y- and z-planes.

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