Simplify distribcell find_offset logic
Simplify distribcell find_offset logic

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