remove unnecessary call to hsync() when closing files
changed hdfs security config keys to hdfs.*
mark instance variables initialized in prepare() as transient
implement locking for file writes/rotation
Implement TimedRotationPolicy
Merge branch 'master' into feature/security-relogin

* master:
  Implement TimedRotationPolicy
  implement locking for file writes/rotation
  mark instance variables initialized in prepare() as transient
  changed hdfs security config keys to hdfs.*
  remove unnecessary call to hsync() when closing files
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Restart worker when RemoteException occurs.