Inconsistent channel state in confirm mode while reconnecting

[makometr]

While testing reconnction behaviour in attemption loop with help of wi-fi connection drop I had managed to send my test message twice by PublishWithDeferredConfirmWithContext. It was possible due to publishConfirms returned after publish were with size 1 and contains nil pointer in publishConfirms[0] (it is check from example). This situation is possible while channel is not in confirm mode. sorry for bad screen

so the next publishing is ok

The Publisher sets a new channel to confirm mode in startPublishHandler function after receiving a reconnect message from the reconnectErrCh channel. The problem is caused that there is a period of time when the channel is ready to send a message, but the publisher has not set the confirm mode yet.

[makometr]

Please refer to PR #188 and feel free to suggest other solutions. I have tried to provide the simplest fix possible.