Write cross section warnings only from master.
Write cross section warnings only from master.

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