Handle producer_ready field when building Producer

[DonghunLouisLee]

According to the official PulsarApi.proto, if producer_ready field is not "ready", the client will avoid to timeout the request for creating the producer. Instead it will wait indefinitely until it gets a subsequent CommandProducerSuccess with producer_ready==true.

This case is not currently handled. Need to check how official java client keeps track of topic_epoch