Don't leave so many threads lying around in the tests

See gh-5141

spring-boot/src/test/java/org/springframework/boot/context/embedded/AbstractEmbeddedServletContainerFactoryTests.java

@@ -170,6 +170,7 @@ public abstract class AbstractEmbeddedServletContainerFactoryTests {
 				.createAsyncRequest(new URI(getLocalUrl("/hello")), HttpMethod.GET)
 				.executeAsync();
 		assertThat(response2.get(10, TimeUnit.SECONDS).getRawStatusCode()).isEqualTo(200);
+		clientHttpRequestFactory.destroy();
 	}
 
 	@Test

spring-boot/src/test/java/org/springframework/boot/jta/bitronix/PoolingDataSourceBeanTests.java

@@ -21,6 +21,7 @@ import java.sql.Connection;
 import javax.sql.XAConnection;
 import javax.sql.XADataSource;
 
+import bitronix.tm.TransactionManagerServices;
 import org.junit.Test;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -72,6 +73,7 @@ public class PoolingDataSourceBeanTests {
 		this.bean.init();
 		this.bean.createPooledConnection(dataSource, this.bean);
 		verify(dataSource).getXAConnection();
+		TransactionManagerServices.getTaskScheduler().shutdown();
 	}
 
 }