Clean up after VOLTHA e2e test

Change-Id: I100a9aef80f75e6be0b9a20e70eacc377c730805
diff --git a/jjb/pipeline/voltha-bbsim-tests.groovy b/jjb/pipeline/voltha-bbsim-tests.groovy
index 08555bc..2cd9340 100644
--- a/jjb/pipeline/voltha-bbsim-tests.groovy
+++ b/jjb/pipeline/voltha-bbsim-tests.groovy
@@ -161,7 +161,7 @@
            fi
          done
          ## clean up node
-	 ./voltha down
+	 WAIT_ON_DOWN=y ./voltha down
 	 cd $WORKSPACE/
 	 rm -rf kind-voltha/ voltha-system-tests/ || true
          '''