use errors.Is() to handle image store errors

The image store's used are an interface, so there's no guarantee
that implementations don't wrap the errors. Make sure to catch
such cases by using errors.Is.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

daemon/images/image_list.go

@@ -2,6 +2,7 @@ package images // import "github.com/docker/docker/daemon/images"
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"sort"
 	"time"
@@ -132,7 +133,7 @@ func (i *ImageService) Images(ctx context.Context, opts types.ImageListOptions)
 			if err != nil {
 				// The layer may have been deleted between the call to `Map()` or
 				// `Heads()` and the call to `Get()`, so we just ignore this error
-				if err == layer.ErrLayerDoesNotExist {
+				if errors.Is(err, layer.ErrLayerDoesNotExist) {
 					continue
 				}
 				return nil, err

image/store.go

@@ -88,7 +88,7 @@ func (is *store) restore() error {
 			}
 			l, err = is.lss.Get(chainID)
 			if err != nil {
-				if err == layer.ErrLayerDoesNotExist {
+				if errors.Is(err, layer.ErrLayerDoesNotExist) {
 					logrus.WithFields(f{"chainID": chainID, "os": img.OperatingSystem(), "err": err}).Error("not restoring image")
 					return nil
 				}

layer/layer_test.go

@@ -2,6 +2,7 @@ package layer // import "github.com/docker/docker/layer"
 
 import (
 	"bytes"
+	"errors"
 	"io"
 	"os"
 	"path/filepath"
@@ -397,7 +398,7 @@ func TestStoreRestore(t *testing.T) {
 	// Create again with same name, should return error
 	if _, err := ls2.CreateRWLayer("some-mount_name", layer3b.ChainID(), nil); err == nil {
 		t.Fatal("Expected error creating mount with same name")
-	} else if err != ErrMountNameConflict {
+	} else if !errors.Is(err, ErrMountNameConflict) {
 		t.Fatal(err)
 	}