Setting the registry in the correct way in the groovy pipelines

Change-Id: I1b81e9c4bb7794c86f2a38b516ab776d06ceedc3
diff --git a/jjb/pipeline/voltha-nightly-tests-bbsim.groovy b/jjb/pipeline/voltha-nightly-tests-bbsim.groovy
index d3c3f13..b2727af 100644
--- a/jjb/pipeline/voltha-nightly-tests-bbsim.groovy
+++ b/jjb/pipeline/voltha-nightly-tests-bbsim.groovy
@@ -98,7 +98,7 @@
              echo "on master, using default settings for kind-voltha"
            fi
 
-           EXTRA_HELM_FLAGS+="--set log_agent.enabled=False ${params.extraHelmFlags} defaults.image_registry=mirror.registry.opennetworking.org/ "
+           EXTRA_HELM_FLAGS+="--set log_agent.enabled=False ${params.extraHelmFlags} --set defaults.image_registry=mirror.registry.opennetworking.org/ "
 
            cd $WORKSPACE/kind-voltha/
            ./voltha up