continue remove image when can't find image id with ref

Signed-off-by: Crazykev <crazykev@zju.edu.cn>

pkg/kubelet/dockershim/docker_image.go

@@ -101,8 +101,11 @@ func (ds *dockerService) RemoveImage(image *runtimeapi.ImageSpec) error {
 			}
 		}
 		return nil
-	} else if err != nil && libdocker.IsImageNotFoundError(err) {
-		return nil
+	}
+	// dockerclient.InspectImageByID doesn't work with digest and repoTags,
+	// it is safe to continue removing it since there is another check below.
+	if err != nil && !libdocker.IsImageNotFoundError(err) {
+		return err
 	}
 
 	_, err = ds.client.RemoveImage(image.Image, dockertypes.ImageRemoveOptions{PruneChildren: true})

pkg/kubelet/dockershim/libdocker/helpers.go

@@ -133,5 +133,8 @@ func matchImageIDOnly(inspected dockertypes.ImageInspect, image string) bool {
 // isImageNotFoundError returns whether the err is caused by image not found in docker
 // TODO: Use native error tester once ImageNotFoundError is supported in docker-engine client(eg. ImageRemove())
 func isImageNotFoundError(err error) bool {
-	return strings.Contains(err.Error(), "No such image:")
+	if err != nil {
+		return strings.Contains(err.Error(), "No such image:")
+	}
+	return false
 }