MAPREDUCE-7158. Inefficient Flush Logic in JobHistory EventWriter. (Zichen Sun via wangda)

Change-Id: I99ace87980da03bb35a8012cea7218d602a8817a
(cherry picked from commit 762a56cc64bc07d57f94e253920534b8e049f238)

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/jobhistory/EventWriter.java

@@ -93,7 +93,6 @@ public class EventWriter {
     wrapper.setType(event.getEventType());
     wrapper.setEvent(event.getDatum());
     writer.write(wrapper, encoder);
-    encoder.flush();
     if (this.jsonOutput) {
       out.writeBytes("\n");
     }