boolean complete() {
            return sslEngine.getHandshakeStatus() == SSLEngineResult.HandshakeStatus.FINISHED ||
                    sslEngine.getHandshakeStatus() == SSLEngineResult.HandshakeStatus.NOT_HANDSHAKING;
        }
Validator used to verify dynamic update of keystore used in inter-broker communication.
The validator checks that a successful handshake can be performed using the keystore and
truststore configured on this SslFactory.
clients/src/main/java/org/apache/kafka/common/security/ssl/SslFactory.java