GH-1452: Close Connection in checkMissingQueues

Resolves #1452

While not a problem with connection factories provided by the framework
(which all ignore `close()`) the code should properly close the connection
after use.

**cherry-pick to 2.4.x, 2.3.x**

spring-rabbit/src/main/java/org/springframework/amqp/rabbit/listener/BlockingQueueConsumer.java

@@ -554,7 +554,8 @@ private void checkMissingQueues() {
 					Connection connection = null; // NOSONAR - RabbitUtils
 					Channel channelForCheck = null;
 					try {
-						channelForCheck = this.connectionFactory.createConnection().createChannel(false);
+						connection = this.connectionFactory.createConnection();
+						channelForCheck = connection.createChannel(false);
 						channelForCheck.queueDeclarePassive(queueToCheck);
 						if (logger.isInfoEnabled()) {
 							logger.info("Queue '" + queueToCheck + "' is now available");