ade-commands: Don't set the same subtest name for both subtests

Let `run-test-in-systemd` figure out the appropriate subtest name when
launching `ade-tests-custom.sh` and `ade-tests-defaults.sh`, instead of
confusingly setting the name as `run-test` for both.

Signed-off-by: Emanuele Aina <emanuele.aina@collabora.com>