testsuite: Make rwtest use the same threshold controls as idiff
testsuite: Make rwtest use the same threshold controls as idiff

cwilling/oiio,bdeluca/oiio,sambler/oiio,OpenImageIO/oiio,mcanthony/oiio,YangYangTL/oiio,cwilling/oiio,cwilling/oiio,OpenImageIO/oiio,lgritz/oiio,sambler/oiio,micler/oiio,scott-wilson/oiio,mcanthony/oiio,mcanthony/oiio,scott-wilson/oiio,YangYangTL/oiio,lgritz/oiio,micler/oiio,OpenImageIO/oiio,sambler/oiio,lgritz/oiio,micler/oiio,bdeluca/oiio,cwilling/oiio,sambler/oiio,bdeluca/oiio,YangYangTL/oiio,lgritz/oiio,scott-wilson/oiio,bdeluca/oiio,YangYangTL/oiio,scott-wilson/oiio,mcanthony/oiio,OpenImageIO/oiio,micler/oiio