Temporarily update voltha-system-tests job to use Khen's VOL-1913 images

Change-Id: I83c97b6a06559f34d2ec2a8b25153a2de7d324bd
diff --git a/jjb/pipeline/voltha-go-tests.groovy b/jjb/pipeline/voltha-go-tests.groovy
index bec890d..d14d398 100644
--- a/jjb/pipeline/voltha-go-tests.groovy
+++ b/jjb/pipeline/voltha-go-tests.groovy
@@ -40,7 +40,7 @@
       steps {
         sh """
            cd kind-voltha/
-           EXTRA_HELM_FLAGS="--set defaults.image_tag=voltha-2.1" VOLTHA_LOG_LEVEL=DEBUG TYPE=minimal WITH_RADIUS=y WITH_BBSIM=y INSTALL_ONOS_APPS=y CONFIG_SADIS=y FANCY=0 ./voltha up
+           EXTRA_HELM_FLAGS="${params.extraHelmFlags}" VOLTHA_LOG_LEVEL=DEBUG TYPE=minimal WITH_RADIUS=y WITH_BBSIM=y INSTALL_ONOS_APPS=y CONFIG_SADIS=y FANCY=0 ./voltha up
            """
       }
     }