Shutdown hook triggers doClose within startupShutdownMonitor

Issue: SPR-13556

spring-context/src/main/java/org/springframework/context/support/AbstractApplicationContext.java

@@ -891,8 +891,10 @@ public abstract class AbstractApplicationContext extends DefaultResourceLoader
 			this.shutdownHook = new Thread() {
 				@Override
 				public void run() {
+					synchronized (startupShutdownMonitor) {
 						doClose();
 					}
+				}
 			};
 			Runtime.getRuntime().addShutdownHook(this.shutdownHook);
 		}