Fix a dual inheritance

Change-Id: I09269ee16df4a889c13335e0c5af14015449d4cf
diff --git a/classes/cluster/drivetrain-ha/cicd/control/slave.yml b/classes/cluster/drivetrain-ha/cicd/control/slave.yml
index f46c1e4..52f21eb 100644
--- a/classes/cluster/drivetrain-ha/cicd/control/slave.yml
+++ b/classes/cluster/drivetrain-ha/cicd/control/slave.yml
@@ -1,3 +1,3 @@
 classes:
-- system.docker.swarm.manager
-- cluster.drivetrain-ha
+  - system.docker.swarm.manager
+  - cluster.drivetrain-ha