Add config for registry http headers

This adds a configuration knob for adding request headers to all
registry requests. It is not namespaced to a registry.

Signed-off-by: Brian Goff <cpuguy83@gmail.com>

pkg/server/image_pull.go

@@ -98,7 +98,8 @@ func (c *criService) PullImage(ctx context.Context, r *runtime.PullImageRequest)
 	}
 	var (
 		resolver = docker.NewResolver(docker.ResolverOptions{
-			Hosts: c.registryHosts(r.GetAuth()),
+			Headers: c.config.Registry.Headers,
+			Hosts:   c.registryHosts(r.GetAuth()),
 		})
 		isSchema1    bool
 		imageHandler containerdimages.HandlerFunc = func(_ context.Context,