messageId attribute of MqttMessage always returns zero

Fix for eclipse-paho/paho.mqtt.android#87

Author: jpwsutton

org.eclipse.paho.client.mqttv3/src/main/java/org/eclipse/paho/client/mqttv3/internal/wire/MqttReceivedMessage.java

@@ -19,14 +19,12 @@
 
 public class MqttReceivedMessage extends MqttMessage {
 
-	private int messageId;
-	
 	public void setMessageId(int msgId) {
-		this.messageId = msgId;
+        	super.setId(msgId);
 	}
-
+	
 	public int getMessageId() {
-		return messageId;
+		return super.getId();
 	}
 
 	// This method exists here to get around the protected visibility of the