[VOL-2782] Update go.mod of voltha-go,open-olt-adapter,ofagent-go and voltctl to be compatible with latest version of voltha-lig-go

Change-Id: Idd1a36b6059927af9a4f3c12581663d587a19176
diff --git a/internal/pkg/core/olt_platform_test.go b/internal/pkg/core/olt_platform_test.go
index 9e2ee56..211459f 100644
--- a/internal/pkg/core/olt_platform_test.go
+++ b/internal/pkg/core/olt_platform_test.go
@@ -324,7 +324,7 @@
 			fu.Output(1),
 		},
 	}
-	ofpstats := fu.MkFlowStat(fa)
+	ofpstats, _ := fu.MkFlowStat(fa)
 	type args struct {
 		flow          *ofp.OfpFlowStats
 		flowDirection string