Add extra vars parameter for cookiecutter/reclass-system test jobs

Add parameter EXTRA_VARIABLES_YAML which will have overrides for
env GERRIT_* parameters from gating job.

Change-Id: I4d639d7857244ed562dcb882c288a49f9ec0523d
Related-Bug: PROD-23343 (PROD:23343)
diff --git a/jenkins/client/job/salt-models/tests.yml b/jenkins/client/job/salt-models/tests.yml
index a7bdbab..c6c54bb 100644
--- a/jenkins/client/job/salt-models/tests.yml
+++ b/jenkins/client/job/salt-models/tests.yml
@@ -227,6 +227,10 @@
               DEFAULT_GIT_REF:
                 type: string
                 default: master
+              EXTRA_VARIABLES_YAML:
+                type: text
+                default: ""
+                description: "Extra vars passed as YAML"
               PARALLEL_NODE_GROUP_SIZE:
                 type: string
                 default: "5"
@@ -294,6 +298,10 @@
               CREDENTIALS_ID:
                 type: string
                 default: gerrit
+              EXTRA_VARIABLES_YAML:
+                type: text
+                default: ""
+                description: "Extra vars passed as YAML"
       job:
         test-salt-model-node:
           name: test-salt-model-node