Sonar fixes

- printStackTrace in test mail server
- Illegal throws
- Large anon. classes

* - indexOf char
- stored external object

* - ignored exceptional return values

* - checkstyle

spring-integration-rsocket/src/main/java/org/springframework/integration/rsocket/outbound/RSocketOutboundGateway.java

@@ -185,12 +185,6 @@ public class RSocketOutboundGateway extends AbstractReplyProducingMessageHandler
 		}
 	}
 
-	@Override
-	public void destroy() {
-		super.destroy();
-
-	}
-
 	@Override
 	protected Object handleRequestMessage(Message<?> requestMessage) {
 		RSocketRequester rsocketRequester = requestMessage.getHeaders()