YARN-4814. ATS 1.5 timelineclient impl call flush after every event write. (Xuan Gong via gtcarrera9)

(cherry picked from commit 3a0b69544183f71c4683bc477656473494fc09d0)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/client/api/impl/FileSystemTimelineWriter.java

@@ -276,6 +276,7 @@ public class FileSystemTimelineWriter extends TimelineWriter{
     mapper.setAnnotationIntrospector(new JaxbAnnotationIntrospector());
     mapper.setSerializationInclusion(Inclusion.NON_NULL);
     mapper.configure(Feature.CLOSE_CLOSEABLE, false);
+    mapper.configure(Feature.FLUSH_AFTER_WRITE_VALUE, false);
     return mapper;
   }