[Test] @AwaitsFix on BootStrapTests.testMixedTriggeredWatchLoading

It seems that it's going to be fixed by elastic/x-pack-elasticsearch#1544.

Original commit: elastic/x-pack-elasticsearch@4dce689b5b

plugin/src/test/java/org/elasticsearch/xpack/watcher/test/integration/BootStrapTests.java

@@ -183,6 +183,7 @@ public class BootStrapTests extends AbstractWatcherIntegrationTestCase {
         });
     }
 
+    @AwaitsFix(bugUrl = "https://github.com/elastic/x-pack-elasticsearch/pull/1544")
     public void testMixedTriggeredWatchLoading() throws Exception {
         createIndex("output");
         client().prepareIndex("my-index", "foo", "bar")