INT-4234: Fix LambdaMessageProcessor logic

JIRA: https://jira.spring.io/browse/INT-4234

When the actual argument type is `Message` there is no reason to go down the `if...else` logic.
This doesn't work for Lambda anyway because of generics erasure in case of `GenericTransformer`, but that is the fix for case of direct interface implementation

spring-integration-core/src/main/java/org/springframework/integration/handler/LambdaMessageProcessor.java

@@ -99,7 +99,7 @@ public class LambdaMessageProcessor implements MessageProcessor<Object>, BeanFac
 			if (Message.class.isAssignableFrom(parameterType)) {
 				args[i] = message;
 			}
-			if (Map.class.isAssignableFrom(parameterType)) {
+			else if (Map.class.isAssignableFrom(parameterType)) {
 				if (message.getPayload() instanceof Map) {
 					args[i] = message.getPayload();
 				}