Move storage package under registry package

Signed-off-by: Stephen J Day <stephen.day@docker.com>

registry/handlers/images.go

@@ -9,7 +9,7 @@ import (
 	ctxu "github.com/docker/distribution/context"
 	"github.com/docker/distribution/digest"
 	"github.com/docker/distribution/manifest"
-	"github.com/docker/distribution/storage"
+	"github.com/docker/distribution/registry/storage"
 	"github.com/gorilla/handlers"
 )