VOL-1643 Update voltha-lib-go to use voltha-protos v3.0.0

and bump up the version to 3.0.0. voltha-protos is modified to be
compatible with the java language proto compilation. It's a major
change and a major version change has been made.

Change-Id: Ifb93430567ddf96aaa0fbf6e5853aad9e1070f6f
diff --git a/pkg/db/backend_test.go b/pkg/db/backend_test.go
index fdd9071..8eae015 100644
--- a/pkg/db/backend_test.go
+++ b/pkg/db/backend_test.go
@@ -18,14 +18,15 @@
 
 import (
 	"context"
-	"github.com/opencord/voltha-lib-go/v2/pkg/mocks"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/opencord/voltha-lib-go/v3/pkg/mocks"
 	"github.com/phayes/freeport"
 	"github.com/stretchr/testify/assert"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
-	"os"
-	"testing"
-	"time"
 )
 
 const (