Prefer AUTOMAKE_fails over `$AUTOMAKE | grep' in tests. * tests/ldadd.test: Enable errexit. Use AUTOMAKE_fails so the verbose log contains all output. * tests/mdate.test: Likewise. Prompted by Stefano Lattarini's change to discover.test. Signed-off-by: Ralf Wildenhues <Ralf.Wildenhues@gmx.de>