[VOL-936] Missing mocks and comments.
Lowering log level for chatty messages

Change-Id: I4012f3e6d8f8c1d11d20dccb81fa182c02265d77
diff --git a/internal/pkg/core/device_handler.go b/internal/pkg/core/device_handler.go
index ba40532..31ad3a2 100644
--- a/internal/pkg/core/device_handler.go
+++ b/internal/pkg/core/device_handler.go
@@ -2182,11 +2182,11 @@
 func (dh *DeviceHandler) getExtValue(device *voltha.Device, value voltha.ValueType_Type) (*voltha.ReturnValues, error) {
 	var err error
 	var ID uint32
+	var sn *oop.SerialNumber
 	resp := new(voltha.ReturnValues)
 	valueparam := new(oop.ValueParam)
 	ctx := context.Background()
 	log.Infow("getExtValue", log.Fields{"onu-id": device.Id, "pon-intf": device.ParentPortNo})
-	sn := new(oop.SerialNumber)
 	if sn, err = dh.deStringifySerialNumber(device.SerialNumber); err != nil {
 		return nil, err
 	}