VOL-2437 Leftover state in etcd after OLT device deleted

Some of the kv store values were not cleared when device is deleted.

 Added APis to clear the kv values once device is deleted.

Change-Id: Id3978206dd4375dd6cb17df2f140d3a9c25cb91b
diff --git a/adaptercore/openolt_flowmgr.go b/adaptercore/openolt_flowmgr.go
index ef6dad5..3376809 100644
--- a/adaptercore/openolt_flowmgr.go
+++ b/adaptercore/openolt_flowmgr.go
@@ -1173,7 +1173,10 @@
 		f.resourceMgr.FreeFlowID(intfID, deviceFlow.OnuId, deviceFlow.UniId, deviceFlow.FlowId)
 		return false
 	}
-	f.registerFlow(logicalFlow, deviceFlow)
+	if deviceFlow.GemportId != -1 {
+		// No need to register the flow if it is a trap on nni flow.
+		f.registerFlow(logicalFlow, deviceFlow)
+	}
 	log.Debugw("Flow added to device successfully ", log.Fields{"flow": *deviceFlow})
 	return true
 }