[SPARK-6314] [CORE] handle JsonParseException for history server

This is handled in the same way with [SPARK-6197](https://issues.apache.org/jira/browse/SPARK-6197). The result of this PR is that exception showed in history server log will be replaced by a warning, and the application that with un-complete history log file will be listed on history server webUI

Author: Zhang, Liye <liye.zhang@intel.com>

Closes #5736 from liyezhang556520/SPARK-6314 and squashes the following commits:

b8d2d88 [Zhang, Liye] handle JsonParseException for history server

core/src/main/scala/org/apache/spark/deploy/history/FsHistoryProvider.scala

@@ -256,8 +256,9 @@ private[history] class FsHistoryProvider(conf: SparkConf) extends ApplicationHis
       }
     try {
       val appListener = new ApplicationEventListener
+      val appCompleted = isApplicationCompleted(eventLog)
       bus.addListener(appListener)
-      bus.replay(logInput, logPath.toString)
+      bus.replay(logInput, logPath.toString, !appCompleted)
       new FsApplicationHistoryInfo(
         logPath.getName(),
         appListener.appId.getOrElse(logPath.getName()),
@@ -266,7 +267,7 @@ private[history] class FsHistoryProvider(conf: SparkConf) extends ApplicationHis
         appListener.endTime.getOrElse(-1L),
         getModificationTime(eventLog).get,
         appListener.sparkUser.getOrElse(NOT_STARTED),
-        isApplicationCompleted(eventLog))
+        appCompleted)
     } finally {
       logInput.close()
     }