Ensure that Jetty is completely stopped when it fails to start

Closes gh-12735

spring-boot/src/main/java/org/springframework/boot/context/embedded/jetty/JettyEmbeddedServletContainer.java

 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 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.
@@ -155,9 +155,11 @@ public class JettyEmbeddedServletContainer implements EmbeddedServletContainer {
 						.info("Jetty started on port(s) " + getActualPortsDescription());
 			}
 			catch (EmbeddedServletContainerException ex) {
+				stopSilently();
 				throw ex;
 			}
 			catch (Exception ex) {
+				stopSilently();
 				throw new EmbeddedServletContainerException(
 						"Unable to start embedded Jetty servlet container", ex);
 			}

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

@@ -357,7 +357,16 @@ public class JettyEmbeddedServletContainerFactoryTests
 
 		});
 		this.thrown.expect(EmbeddedServletContainerException.class);
-		factory.getEmbeddedServletContainer().start();
+		JettyEmbeddedServletContainer jettyContainer = (JettyEmbeddedServletContainer) factory
+				.getEmbeddedServletContainer();
+		try {
+			jettyContainer.start();
+		}
+		finally {
+			QueuedThreadPool threadPool = (QueuedThreadPool) jettyContainer.getServer()
+					.getThreadPool();
+			assertThat(threadPool.isRunning()).isFalse();
+		}
 	}
 
 	@Test