sp-cinder: Add missing key

Change-Id: If84250987b1b11d542126f8a7d5a8b15b1d0ac62
diff --git a/zuul.d/sp-cinder.yaml b/zuul.d/sp-cinder.yaml
index 78c08ee..aab46e1 100644
--- a/zuul.d/sp-cinder.yaml
+++ b/zuul.d/sp-cinder.yaml
@@ -33,8 +33,9 @@
         ENABLE_VOLUME_MULTIATTACH: true
       devstack_local_conf:
         test-config:
-          validation:
-            run_validation: true
+          $TEMPEST_CONFIG:
+            validation:
+              run_validation: true
         post-config:
           $CINDER_CONF:
             storpool: