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/values.yaml b/xos-profiles/ponsim-pod/values.yaml
index 14353e9..01a7d70 100644
--- a/xos-profiles/ponsim-pod/values.yaml
+++ b/xos-profiles/ponsim-pod/values.yaml
@@ -55,3 +55,7 @@
   - of:00000da7f2c143c7
   - of:000032be2d4c2abc
   - of:0000ae9b8dcd58c7
+
+fabric:
+  stratum:
+    enabled: false