Incorrect casting in v5 ClientState persistBufferedMessage

[Jugen]

The two MqttPublish casts in the following piece of code should be changed to MqttPersistable otherwise subscribe and unsubsribed messages throw ClassCastException

paho.mqtt.java/org.eclipse.paho.mqttv5.client/src/main/java/org/eclipse/paho/mqttv5/client/internal/ClientState.java

Lines 616 to 623 in 9c742c1

	try {
	persistence.put(key, (MqttPublish) message);
	} catch (MqttPersistenceException mpe) {
	// @TRACE 515=Could not Persist, attempting to Re-Open Persistence Store
	log.fine(CLASS_NAME, methodName, "515");
	persistence.open(this.clientComms.getClient().getClientId());
	persistence.put(key, (MqttPublish) message);
	}