Added Consumer handling for single message NACK/requeue

When using ConsumerInterface::MSG_REJECT_REQUEUE, the message will requeue but will not be redelivered to the same consumer. This can cause messages to get stuck in a one consumer configuration. Using NACK/requeue, the message is requeued and will be redelivered back to the same consumer once again. This behavior is strange... afaik, on an AMQP level, there are no differences between a reject and a single message nack.