Use the 'gerrit' choosing-strategy so code is properly checked

Change-Id: I73634002cb6732d7bc4662ef97d784a4dc4563b9
diff --git a/jjb/siab-e2e.yaml b/jjb/siab-e2e.yaml
index ee8e720..6a902ec 100644
--- a/jjb/siab-e2e.yaml
+++ b/jjb/siab-e2e.yaml
@@ -36,7 +36,7 @@
           refspec: '{refspec}'
           branch: '{branch}'
           submodule-recursive: 'false'
-          choosing-strategy: default
+          choosing-strategy: 'gerrit'
           jenkins-ssh-credential: '{jenkins-ssh-credential}'
           basedir: 'cord/automation-tools'