Set minimal concurrency for periodic jobs

Change-Id: Ibdda673838fb8cd52d828dade0e19584b42edccd
Related-Prod: 17361
diff --git a/jenkins/client/job/oscore/tests.yml b/jenkins/client/job/oscore/tests.yml
index 06060bd..705d83b 100644
--- a/jenkins/client/job/oscore/tests.yml
+++ b/jenkins/client/job/oscore/tests.yml
@@ -252,7 +252,7 @@
               TEST_TEMPEST_PATTERN:
                 type: string
                 description: Run tests matched to pattern only
-                default: "tempest"
+                default: "tempest --concurrency 2"
               TEST_MODEL:
                 type: string
                 description: Environment salt model