Using -ingester.ingester.max-transfer-retries with zero value ends with unexpected (?) result

One would assume that setting `-ingester.ingester.max-transfer-retries` to zero disables transfers, when in fact it enables infinite number of retries instead. This should either be documented or fixed.

Reason for this behaviour is that -ingester.ingester.max-transfer-retries value is passed as `MaxRetries` in `BackOffConfig` struct, where zero means infinite retries.