TEST-74-AUX-UTILS: check for failed units after capsule test

TEST-74-AUX-UTILS: check for failed units after capsule test

TEST-74-AUX-UTILS has a number of subtests.
test/units/TEST-74-AUX-UTILS.capsule.sh runs first and starts and stops
capsule@foobar.service. Looking at the test, the unit is cleanly stopped.
But later test/units/TEST-74-AUX-UTILS.machine-id-setup.sh tests for
failed units. capsule@foobar.service is listed as failed, causing the
second subtest to fail.

Add the same test in test/units/TEST-74-AUX-UTILS.capsule.sh to see
if the failed test really originates from there.