Add SALT_MODELS_SYSTEM_REF_CHANGE parameter for E\\ deployments

PROD-36517

Change-Id: I5fb0cfc828cccc67dccf841d307827d9e649cab2
diff --git a/jobs/templates/bm-e7-cicd-pike-ovs-maas.yml b/jobs/templates/bm-e7-cicd-pike-ovs-maas.yml
index b0feb54..d8de8b1 100644
--- a/jobs/templates/bm-e7-cicd-pike-ovs-maas.yml
+++ b/jobs/templates/bm-e7-cicd-pike-ovs-maas.yml
@@ -70,6 +70,11 @@
         name: TCP_QA_REFS
         trim: 'false'
     - string:
+        default: ''
+        description: ''
+        name: SALT_MODELS_SYSTEM_REF_CHANGE
+        trim: 'false'
+    - string:
         default: refs/heads/release/2019.2.0
         description: reference to patchset in pipeline-library
         name: PIPELINE_LIBRARY_REF