SEBA-564 Use Mininet image with OvS 2.9.0 for QinQ matching

Change-Id: I75e710747ebfc9d91a6352ce9999770ffd74d4eb
diff --git a/mininet/values.yaml b/mininet/values.yaml
index 32a6fea..3670bef 100644
--- a/mininet/values.yaml
+++ b/mininet/values.yaml
@@ -23,7 +23,7 @@
 
 image:
   repository: ciena/mininet
-  tag: latest
+  tag: ubuntu-bionic
   pullPolicy: IfNotPresent
 
 resources: {}
@@ -49,3 +49,4 @@
   cni: "calico,pon1"
 
 onosOpenflowSvc: "onos-openflow.default.svc.cluster.local"
+vlanMatchDepth: 2