Some error logs are confusing

[amyangfei]

Please answer these questions before submitting your issue. Thanks!

1. What did you do?

br/pkg/backup/push.go

Lines 96 to 103 in 8ffad37

	errPb := resp.GetError()
	switch v := errPb.Detail.(type) {
	case *backup.Error_KvError:
	log.Error("backup occur kv error", zap.Reflect("error", v))
	case *backup.Error_RegionError:
	log.Error("backup occur region error",
	zap.Reflect("error", v))

Is the error backup.Error_KvError and backup.Error_RegionError retryable? If so, error log may be confused.

2. What did you expect to see?

3. What did you see instead?

4. What version of BR and TiDB/TiKV/PD are you using?

[3pointer]

Yes, these errors are retryable. I think we can change log level to warn.