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/xos-profiles/ponsim-pod/tosca/020-pod-olt.yaml b/xos-profiles/ponsim-pod/tosca/020-pod-olt.yaml
index 9398a65..74262d4 100644
--- a/xos-profiles/ponsim-pod/tosca/020-pod-olt.yaml
+++ b/xos-profiles/ponsim-pod/tosca/020-pod-olt.yaml
@@ -41,7 +41,11 @@
         device_type: ponsim_olt
         host: olt{{ $i }}.voltha.svc
         port: 50060
+{{- if not $.Values.fabric.stratum.enabled }}
         switch_datapath_id: of:0000000000000001
+{{- else }}
+        switch_datapath_id: device:agg1
+{{- end }}
         switch_port: "{{ add 2 $i }}"
         outer_tpid: "0x8100"
 {{- if $.Values.bandwidthProfiles }}