c8d/inspect: Ignore manifest with missing config

Fix a failure to inspect image if any of its present manifest references
an image config which isn't present locally.

Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>
(cherry picked from commit 5767330)
Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>

daemon/containerd/image.go

@@ -48,11 +48,19 @@ func (i *ImageService) GetImage(ctx context.Context, refOrID string, options ima
 	err = i.walkImageManifests(ctx, desc, func(img *ImageManifest) error {
 		conf, err := img.Config(ctx)
 		if err != nil {
-			return err
+			return fmt.Errorf("failed to get config descriptor: %w", err)
 		}
+
 		var ociimage ocispec.Image
 		if err := readConfig(ctx, cs, conf, &ociimage); err != nil {
-			return err
+			if cerrdefs.IsNotFound(err) {
+				log.G(ctx).WithFields(log.Fields{
+					"manifestDescriptor": img.Target(),
+					"configDescriptor":   conf,
+				}).Debug("manifest present, but its config is missing, ignoring")
+				return nil
+			}
+			return fmt.Errorf("failed to read config of the manifest %v: %w", img.Target().Digest, err)
 		}
 		presentImages = append(presentImages, ociimage)
 		return nil
@@ -61,7 +69,8 @@ func (i *ImageService) GetImage(ctx context.Context, refOrID string, options ima
 		return nil, err
 	}
 	if len(presentImages) == 0 {
-		return nil, errdefs.NotFound(errors.New("failed to find image manifest"))
+		ref, _ := reference.ParseAnyReference(refOrID)
+		return nil, images.ErrImageDoesNotExist{Ref: ref}
 	}
 
 	sort.SliceStable(presentImages, func(i, j int) bool {