Exponential backoff for reconnect does not work

When a client connects to a SSL listener using PLAINTEXT security protocol, after the TCP connection is setup, the client considers the channel setup is complete (in reality the channel setup is not complete yet). The client issues API version request after that. When issuing API version request, reconnection exponential backoff is reset. Since the broker expects SSL handshake, client's API version request will cause the connection to disconnect. Reconnect will happen without exponential backoff since it has been reset.

https://github.com/apache/kafka/blob/trunk/clients/src/main/java/org/apache/kafka/clients/ClusterConnectionStates.java#L249.