Require a base job

This makes base jobs required and allows for a per-tenant default.

Story: 2001110
Task: 4793
Change-Id: I26ffddad8358c156cfac749ce98af70f3447f671
diff --git a/tests/fixtures/layouts/repo-checkout-timer-override.yaml b/tests/fixtures/layouts/repo-checkout-timer-override.yaml
index 594d74c..99fc4f5 100644
--- a/tests/fixtures/layouts/repo-checkout-timer-override.yaml
+++ b/tests/fixtures/layouts/repo-checkout-timer-override.yaml
@@ -6,6 +6,10 @@
         - time: '* * * * * */1'
 
 - job:
+    name: base
+    parent: null
+
+- job:
     name: integration
     branches: master
     override-branch: stable/havana