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/reporting-multiple-github.yaml b/tests/fixtures/layouts/reporting-multiple-github.yaml
index 22fa1e7..0126ec5 100644
--- a/tests/fixtures/layouts/reporting-multiple-github.yaml
+++ b/tests/fixtures/layouts/reporting-multiple-github.yaml
@@ -23,7 +23,12 @@
         status: 'success'
 
 - job:
+    name: base
+    parent: null
+
+- job:
     name: project1-test1
+
 - job:
     name: project2-test2