govet: suppress warning about Parent field that repeated json tag "parent"
```
image/image.go:65:2: structtag: struct field Parent repeats json tag "parent" also at image.go:39 (govet)
Parent     ID        `json:"parent,omitempty"`
```
@@ -62,7 +62,7 @@ type V1Image struct {
// Image stores the image configuration
type Image struct {
V1Image
- Parent ID `json:"parent,omitempty"`
+ Parent ID `json:"parent,omitempty"` //nolint:govet
RootFS *RootFS `json:"rootfs,omitempty"`
History []History `json:"history,omitempty"`
OSVersion string `json:"os.version,omitempty"`
