Discard old tarballs from testing cookiecutter's jobs

Change-Id: I58d26c69f5758d4038408f4b6b8c57ef8bcbc088
diff --git a/jenkins/client/job/salt-models/tests.yml b/jenkins/client/job/salt-models/tests.yml
index dd2ca90..e10339f 100644
--- a/jenkins/client/job/salt-models/tests.yml
+++ b/jenkins/client/job/salt-models/tests.yml
@@ -103,6 +103,11 @@
           jobs:
             - cookiecutter_template: cookiecutter-templates
           template:
+            discard:
+             build:
+               keep_num: 20
+             artifact:
+               keep_num: 20
             type: workflow-scm
             concurrent: true
             scm: