[SMALLFIX] Java 8 migration: replace anonymous type with lambda in alluxio.web.WebInterfaceBrowseLogsServlet#LOG_FILE_FILTER

[newnius]

Replace

  private static final FilenameFilter LOG_FILE_FILTER = new FilenameFilter() {
    @Override
    public boolean accept(File dir, String name) {
      return name.toLowerCase().endsWith(".log");
    }
  };

with

  private static final FilenameFilter LOG_FILE_FILTER = (dir, name) -> name.toLowerCase().endsWith(".log");