Revert "[VOL-4518] remove flowKey and use only flowID for OLT and ONU flow cache since flowID's are unique"

This reverts commit d444598f453757cc0b9fb4ad7295dc1726a69c3f.

Change-Id: I449099e083d363db5834dc6c56330af3fd0ce921
diff --git a/internal/bbsim/devices/onu_state_machine_test.go b/internal/bbsim/devices/onu_state_machine_test.go
index a324d81..c1f6d8e 100644
--- a/internal/bbsim/devices/onu_state_machine_test.go
+++ b/internal/bbsim/devices/onu_state_machine_test.go
@@ -40,7 +40,10 @@
 	onu.InternalState.SetState(OnuStateEnabled)
 	assert.Equal(t, onu.InternalState.Current(), OnuStateEnabled)
 
-	onu.FlowIds = []uint64{1, 2}
+	onu.Flows = []FlowKey{
+		{ID: 1, Direction: "upstream"},
+		{ID: 2, Direction: "downstream"},
+	}
 	key := omcilib.OnuAlarmInfoMapKey{
 		MeInstance: 257,
 		MeClassID:  me.PhysicalPathTerminationPointEthernetUniClassID,
@@ -54,7 +57,7 @@
 	assert.Equal(t, onu.InternalState.Current(), OnuStateDisabled)
 
 	assert.Equal(t, len(onu.onuAlarmsInfo), 0)
-	assert.Equal(t, len(onu.FlowIds), 0)
+	assert.Equal(t, len(onu.Flows), 0)
 	assert.Equal(t, len(onu.PonPort.AllocatedOnuIds), 0)
 	assert.Equal(t, len(onu.PonPort.AllocatedAllocIds), 0)
 	assert.Equal(t, len(onu.PonPort.AllocatedGemPorts), 0)