VOL-2192 Update the OnuId to the one received from voltha during discovery

Change-Id: I3fb759fc4422a58428ec3a8cb7e35dd5ac26fca0
diff --git a/internal/bbsim/devices/olt.go b/internal/bbsim/devices/olt.go
index c374d4a..6b15de4 100644
--- a/internal/bbsim/devices/olt.go
+++ b/internal/bbsim/devices/olt.go
@@ -490,6 +490,7 @@
 
 	pon, _ := o.GetPonById(onu.IntfId)
 	_onu, _ := pon.GetOnuBySn(onu.SerialNumber)
+	_onu.SetID(onu.OnuId)
 
 	if err := _onu.OperState.Event("enable"); err != nil {
 		oltLogger.WithFields(log.Fields{