Stop endpoints in the end of tests

https://build.spring.io/browse/INT-MASTERSPRING40-954/

The `ReactiveStreamsConsumerTests` fails with some race condition from time to time.
Possible reason that no one endpoint is stopped in the end of test.
Even if we step out from the test method, background threads are still active

spring-integration-core/src/test/java/org/springframework/integration/channel/reactive/ReactiveStreamsConsumerTests.java

@@ -99,6 +99,8 @@ public void testReactiveStreamsConsumerFluxMessageChannel() throws InterruptedEx
 
 		assertThat(stopLatch.await(10, TimeUnit.SECONDS)).isTrue();
 		assertThat(result).containsExactly(testMessage, testMessage2);
+
+		reactiveConsumer.stop();
 	}
 
 
@@ -222,6 +224,8 @@ public void testReactiveStreamsConsumerPollableChannel() throws InterruptedExcep
 		verify(testSubscriber, never()).onComplete();
 
 		assertThat(messages.isEmpty()).isTrue();
+
+		reactiveConsumer.stop();
 	}
 
 	@Test
@@ -264,6 +268,8 @@ public void testReactiveStreamsConsumerViaConsumerEndpointFactoryBean() throws E
 		assertThat(stopLatch.await(10, TimeUnit.SECONDS)).isTrue();
 		assertThat(result.size()).isEqualTo(3);
 		assertThat(result).containsExactly(testMessage, testMessage2, testMessage2);
+
+		endpointFactoryBean.stop();
 	}
 
 	@Test
@@ -302,7 +308,8 @@ public void testReactiveStreamsConsumerFluxMessageChannelReactiveMessageHandler(
 				.expectNext(testMessage, testMessage2)
 				.thenCancel()
 				.verify();
-	}
 
+		reactiveConsumer.stop();
+	}
 
 }