Don't fail tests if no tests present

If the project has no tests, don't consider that a failure.  This
way we can run "bazelisk test plugins/foo/..." and it will succeed
if the plugin has no tests.

Bazelisk apparently return RC 4 in that case.

Change-Id: I274bdf78f5d9dc953aa335dc2d694e213a03a2aa
diff --git a/roles/bazelisk-build/tasks/main.yaml b/roles/bazelisk-build/tasks/main.yaml
index d3a6615..987c390 100644
--- a/roles/bazelisk-build/tasks/main.yaml
+++ b/roles/bazelisk-build/tasks/main.yaml
@@ -13,3 +13,5 @@
   args:
     executable: /bin/bash
     chdir: "{{ zuul_work_dir }}"
+  register: test_result
+  failed_when: test_result.rc not in [0, 4]
diff --git a/zuul.d/test-jobs.yaml b/zuul.d/test-jobs.yaml
index 0cdd6ce..b31c86c 100644
--- a/zuul.d/test-jobs.yaml
+++ b/zuul.d/test-jobs.yaml
@@ -50,9 +50,9 @@
     name: test-gerrit-plugin-build
     parent: gerrit-plugin-build
     required-projects:
-      - plugins/checks
+      - plugins/gitiles
     vars:
-      gerrit_plugin: checks
+      gerrit_plugin: gitiles
     files:
       - roles/ensure-bazelisk/.*
       - roles/prepare-gerrit-repos/.*