Add internal noop job

It does nothing.  Successfully.

This can be used in cases where a gate pipeline is required to
merge changes, but a project has no jobs to run.  This will
run a fake internal job that succeeds without wasting any worker
resources.

Change-Id: Ica0d109aaae5fd9aff6485eaba9c428491f98c60
diff --git a/tests/fixtures/layout-no-jobs.yaml b/tests/fixtures/layout-no-jobs.yaml
index ee8dc62..e860ad5 100644
--- a/tests/fixtures/layout-no-jobs.yaml
+++ b/tests/fixtures/layout-no-jobs.yaml
@@ -38,6 +38,6 @@
   - name: org/project
     merge-mode: cherry-pick
     check:
-      - noop
+      - gate-noop
     gate:
-      - noop
+      - gate-noop