tests: conditionalize return code on chg in test-config.t If there is any error while reading config, chg just returns 255 instead of 30. It seems to me that we cannot conditionalize only return codes in output using trailing `(chg !)` and hence used testcases. The test was failing with chg but after this patch, it now passes. Differential Revision: https://phab.mercurial-scm.org/D9463