Add support for running SiaB with stratum_bmv2 as the fabric switch

- new value file (seba-ponsim-stratum.yaml) to deploy SiaB with Stratum
- new mininet script to use stratum_bmv2 instead of OVS as Fabric switch
- update to ponsim and mininet to use the new Stratum device instead of OVS

Change-Id: I35901b455865cebc0a11de8b155b951e4fa4a9f8
diff --git a/mininet/values.yaml b/mininet/values.yaml
index 1515347..1916755 100644
--- a/mininet/values.yaml
+++ b/mininet/values.yaml
@@ -49,6 +49,8 @@
             - olt
         topologyKey: kubernetes.io/hostname
 
+stratumEnabled: false
+topoScript: '/toposcripts/topo.py'
 onosOpenflowSvc: "onos-openflow.default.svc.cluster.local"
 vlanMatchDepth: 2
 enableMulticast: true