Replace close method with Undertow exchange listener

The Undertow HttpServerExchange has a complete listener which we can
use instead of the close() method UndertowServerHttpRequest.

spring-web/src/main/java/org/springframework/http/server/reactive/UndertowHttpHandlerAdapter.java

@@ -76,13 +76,11 @@ public class UndertowHttpHandlerAdapter extends HttpHandlerAdapterSupport
 				if (!exchange.isResponseStarted() && exchange.getStatusCode() <= 500) {
 					exchange.setStatusCode(500);
 				}
-				request.close();
 				exchange.endExchange();
 			}
 			@Override
 			public void onComplete() {
 				logger.debug("Successfully completed request");
-				request.close();
 				exchange.endExchange();
 			}
 		});

spring-web/src/main/java/org/springframework/http/server/reactive/UndertowServerHttpRequest.java

@@ -58,7 +58,7 @@ public class UndertowServerHttpRequest extends AbstractServerHttpRequest {
 		super(initUri(exchange), initHeaders(exchange));
 		this.exchange = exchange;
 		this.body = new RequestBodyPublisher(exchange, dataBufferFactory);
-		this.body.registerListener();
+		this.body.registerListener(exchange);
 	}
 
 	private static URI initUri(HttpServerExchange exchange) {
@@ -107,9 +107,6 @@ public class UndertowServerHttpRequest extends AbstractServerHttpRequest {
 		return Flux.from(this.body);
 	}
 
-	void close() {
-		this.body.onAllDataRead();
-	}
 
 	private static class RequestBodyPublisher extends AbstractListenerReadPublisher<DataBuffer> {
 
@@ -134,7 +131,11 @@ public class UndertowServerHttpRequest extends AbstractServerHttpRequest {
 			this.dataBufferFactory = dataBufferFactory;
 		}
 
-		private void registerListener() {
+		private void registerListener(HttpServerExchange exchange) {
+			exchange.addExchangeCompleteListener((ex, next) -> {
+				onAllDataRead();
+				next.proceed();
+			});
 			this.requestChannel.getReadSetter().set(this.readListener);
 			this.requestChannel.getCloseSetter().set(this.closeListener);
 			this.requestChannel.resumeReads();