Parse the entire history file and populate the JobInfo object
   * The first invocation will populate the object, subsequent calls
   * will return the already parsed object. 
   * The input stream is closed on return
Parse the entire history file and populate the JobInfo object
   * The first invocation will populate the object, subsequent calls
   * will return the already parsed object. 
   * The input stream is closed on return | JobHistoryParser.java