cli/registry: fix a Debugf statement

Fix this warning from go-1.11

> cli/registry/client/fetcher.go:234: Debugf format %s has arg
> repoEndpoint of wrong type client.repositoryEndpoint

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
(cherry picked from commit 51848bf3bb)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

cli/registry/client/fetcher.go

@@ -231,7 +231,7 @@ func (c *client) iterateEndpoints(ctx context.Context, namedRef reference.Named,
 		repoEndpoint := repositoryEndpoint{endpoint: endpoint, info: repoInfo}
 		repo, err := c.getRepositoryForReference(ctx, namedRef, repoEndpoint)
 		if err != nil {
-			logrus.Debugf("error with repo endpoint %s: %s", repoEndpoint, err)
+			logrus.Debugf("error %s with repo endpoint %+v", err, repoEndpoint)
 			if _, ok := err.(ErrHTTPProto); ok {
 				continue
 			}