VOLTHA/VOL-3478 : FlowId are logged as decimals and reported by voltctl as hex.

By Default flow-id would be in int format .
hex-id option is supported to display flow id in hex format.

Change-Id: I8b715613a6800b89a5dcedb8b90dc289b336bf24
diff --git a/pkg/model/flow.go b/pkg/model/flow.go
index 1a5f88b..928339c 100644
--- a/pkg/model/flow.go
+++ b/pkg/model/flow.go
@@ -294,10 +294,15 @@
 	return fmt.Sprintf("%d", val)
 }
 
-func (f *Flow) PopulateFromProto(flow *openflow_13.OfpFlowStats) {
+func (f *Flow) PopulateFromProto(flow *openflow_13.OfpFlowStats, hexId bool) {
 
 	f.Reset()
-	f.Id = fmt.Sprintf("%016x", flow.Id)
+	if hexId {
+		f.Id = fmt.Sprintf("%016x", flow.Id)
+	} else {
+		f.Id = fmt.Sprintf("%v", flow.Id)
+	}
+
 	f.TableId = flow.TableId
 	f.Priority = flow.Priority
 	// mask the lower 8 for the cookie, why?