Fix ContentEnricherTests for dangling threads

https://build.spring.io/browse/INT-MJATS41-1353/

**Cherry-pick to 5.0.x and 4.3.x**

(cherry picked from commit 5e73919)

Author: artembilan

spring-integration-core/src/test/java/org/springframework/integration/transformer/ContentEnricherTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -30,7 +30,6 @@
 import java.util.HashMap;
 import java.util.Map;
 
-import org.junit.Before;
 import org.junit.Test;
 
 import org.springframework.beans.factory.BeanFactory;
@@ -64,14 +63,6 @@
  */
 public class ContentEnricherTests {
 
-	private final ThreadPoolTaskScheduler taskScheduler = new ThreadPoolTaskScheduler();
-
-	@Before
-	public void init() throws Exception {
-		taskScheduler.setPoolSize(2);
-		taskScheduler.afterPropertiesSet();
-	}
-
 	/**
 	 * In this test a {@link Target} message is passed into a {@link ContentEnricher}.
 	 * The Enricher passes the message to a "request-channel" that is backed by a
@@ -137,6 +128,11 @@ protected Object handleRequestMessage(Message<?> requestMessage) {
 
 		consumer.setTrigger(new PeriodicTrigger(0));
 		consumer.setErrorHandler(errorHandler);
+
+		ThreadPoolTaskScheduler taskScheduler = new ThreadPoolTaskScheduler();
+		taskScheduler.setPoolSize(2);
+		taskScheduler.afterPropertiesSet();
+
 		consumer.setTaskScheduler(taskScheduler);
 		consumer.setBeanFactory(mock(BeanFactory.class));
 		consumer.afterPropertiesSet();
@@ -153,6 +149,10 @@ protected Object handleRequestMessage(Message<?> requestMessage) {
 					e.getMessage());
 			return;
 		}
+		finally {
+			consumer.stop();
+			taskScheduler.destroy();
+		}
 
 		fail("ReplyRequiredException expected.");
 
@@ -469,6 +469,8 @@ protected Object handleRequestMessage(Message<?> requestMessage) {
 		assertFalse(enricher.isRunning());
 		enricher.start();
 		assertTrue(enricher.isRunning());
+
+		enricher.stop();
 	}
 
 	/**