Ignore AlreadyClosedException in SimpleConnection

**cherry-pick to 2.1.x**

Author: garyrussell

spring-rabbit/src/main/java/org/springframework/amqp/rabbit/connection/SimpleConnection.java

@@ -23,6 +23,7 @@
 import org.springframework.amqp.rabbit.support.RabbitExceptionTranslator;
 import org.springframework.util.ObjectUtils;
 
+import com.rabbitmq.client.AlreadyClosedException;
 import com.rabbitmq.client.BlockedListener;
 import com.rabbitmq.client.Channel;
 import com.rabbitmq.client.impl.NetworkConnection;
@@ -76,6 +77,9 @@ public void close() {
 			// let the physical close time out if necessary
 			this.delegate.close(this.closeTimeout);
 		}
+		catch (AlreadyClosedException e) {
+			// Ignore
+		}
 		catch (IOException e) {
 			throw RabbitExceptionTranslator.convertRabbitAccessException(e);
 		}