Added job throttle categories to the test salt models and formulas Jenkins jobs

Change-Id: Ic273bcf79fd152e1102a92766f9e7b4bf2efcf02
diff --git a/jenkins/client/job/salt-formulas/tests.yml b/jenkins/client/job/salt-formulas/tests.yml
index c8985ed..e74e43c 100644
--- a/jenkins/client/job/salt-formulas/tests.yml
+++ b/jenkins/client/job/salt-formulas/tests.yml
@@ -181,6 +181,12 @@
               keep_num: 10
           type: workflow-scm
           concurrent: true
+          plugin_properties:
+            throttleconcurrents:
+              enabled: true
+              throttle_option: category
+              categories:
+                - test-formula
           scm:
             type: git
             url: "${_param:jenkins_gerrit_url}/mk/mk-pipelines"