private SslSender createSender(String tlsProtocol, InetSocketAddress serverAddress, byte[] payload) {
        return new SslSender(tlsProtocol, serverAddress, payload);
    }
Connects and waits for handshake to complete. This is required since SslTransportLayer
implementation requires the channel to be ready before send is invoked (unlike plaintext
where send can be invoked straight after connect)
clients/src/test/java/org/apache/kafka/common/network/SslSelectorTest.java