Update FsHistoryProvider.scala

As describe In SPARK-3697 HistoryServer cann't list event Log on WEB UI when there was a no permissions directory in the $spark.eventLog.dir. eg, The following files list is in the $spark.eventLog.dir
Because the HistoryServer don't have permission to read the directory(/spark-logs/eventLog/simple-application-1411720159090). and lead the HistoryServer cann't show other event log file on the WEB UI. but show "No Completed Applications Found"! I think the HistoryServer can ignore the incorrect directory(eg: /spark-logs/eventLog/simple-application-1411720159090 as mentioned above).