Don't use messageIds when publishes cannot be sent (#318)

When maxInflight is reached all new messages do get a message id. At some point
the available messageids will get exausted resulting in even bigger issues
This patch prevents messageids from being exausted by reclaiming them for
undoed messages

Signed-off-by: Hmvp <github@hmvp.nl>

Author: hmvp

org.eclipse.paho.client.mqttv3/src/main/java/org/eclipse/paho/client/mqttv3/internal/ClientState.java

@@ -615,6 +615,13 @@ protected void undo(MqttPublish message) throws MqttPersistenceException {
 			pendingMessages.removeElement(message);
 			persistence.remove(getSendPersistenceKey(message));
 			tokenStore.removeToken(message);
+			if(message.getMessage().getQos() > 0){
+				//Free this message Id so it can be used again
+				releaseMessageId(message.getMessageId());
+				//Set the messageId to 0 so if it's ever retried, it will get a new messageId
+				message.setMessageId(0);
+			}
+
 			checkQuiesceLock();
 		}
 	}