functional-tests: Fix failed tests being reported as successful

Due to a mistake in the test runner, it was possible for tests to
fail but appear to have succeeded.
1 job for <span class="ref-name">sam/test-runner-fix</span> in 1 minute and 9 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
failed #211883
test-fedora-latest

00:01:09

 
Name Stage Failure
failed
test-fedora-latest Test

----------------------------------------------------------------------
Ran 1 test in 8.953s

FAILED (errors=1)
-------

Full log written to /builds/GNOME/tracker-miners/build/meson-logs/testlog.txt
ERROR: Job failed: exit code 1