Fix javadoc

Closes gh-8892

spring-boot/src/main/java/org/springframework/boot/admin/SpringApplicationAdminMXBean.java

 /*
- * Copyright 2012-2015 the original author or authors.
+ * Copyright 2012-2017 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.
@@ -33,9 +33,9 @@ public interface SpringApplicationAdminMXBean {
 	boolean isReady();
 
 	/**
-	 * Specify if the application runs in an embedded web container. Can return
-	 * {@code null} if that information is not yet available. It is preferable to wait for
-	 * the application to be {@link #isReady() ready}.
+	 * Specify if the application runs in an embedded web container. Return
+	 * {@code false} on a web application that hasn't fully started yet, so it is
+	 * preferable to wait for the application to be {@link #isReady() ready}.
 	 * @return {@code true} if the application runs in an embedded web container
 	 * @see #isReady()
 	 */