[VOL-4552] Test FTTB support in BBSIM

Change-Id: I5d2ccf3345de1989c13e3c4b9d84f23d04a41df6
diff --git a/internal/bbsim/devices/onu.go b/internal/bbsim/devices/onu.go
index 845067a..f7d2171 100644
--- a/internal/bbsim/devices/onu.go
+++ b/internal/bbsim/devices/onu.go
@@ -1664,7 +1664,7 @@
 		OnuId:         int32(o.ID),
 		UniId:         int32(0), // NOTE do not hardcode this, we need to support multiple UNIs
 		FlowId:        uint64(o.ID),
-		FlowType:      "downstream",
+		FlowType:      flowTypeDownstream,
 		NetworkIntfId: int32(0),
 		Classifier:    &classifierProto,
 		Action:        &actionProto,
@@ -1715,7 +1715,7 @@
 		OnuId:         int32(o.ID),
 		UniId:         int32(0), // BBR only supports a single UNI
 		FlowId:        uint64(o.ID),
-		FlowType:      "downstream",
+		FlowType:      flowTypeDownstream,
 		NetworkIntfId: int32(0),
 		Classifier:    &classifierProto,
 		Action:        &actionProto,