tests/chmod: refactor tests to only create reference file once
tests/chmod: refactor tests to only create reference file once

Heather/coreutils,wimh/coreutils,ebfe/coreutils,wimh/coreutils,tempbottle/coreutils,uutils/coreutils,kwantam/coreutils,keunwoo/coreutils,Heather/coreutils,Arcterus/coreutils,keunwoo/coreutils,kevgeniy/coreutils,tempbottle/coreutils,ebfe/coreutils,Arcterus/coreutils,jbcrail/coreutils,uutils/coreutils,kevgeniy/coreutils,jbcrail/coreutils,uutils/coreutils,kwantam/coreutils