static void cleanup(String file) throws IOException {
    try {
      Files.delete(FileSystems.getDefault().getPath(file));
    } catch (NoSuchFileException nsfe) {
      LOG.warn("FileNotFoundException for {}", file, nsfe);
    }
  }
Create rule file with empty rules.
@param file Name of file to write rules into.
@return Full file name of the rules file which is <code>dir</code> + DEFAULT_RULES_FILE_NAME.
hbase-balancer/src/test/java/org/apache/hadoop/hbase/master/balancer/HeterogeneousCostRulesTestHelper.java