Add the missing --reap statements in innodb_bug38231.test. Probably MySQL
enforced the presence of those recently and the test started failing like:

  main.innodb_bug38231                     [ fail ]
          Test ended at 2010-03-10 08:48:32
  
  CURRENT_TEST: main.innodb_bug38231
  mysqltest: At line 49: Cannot run query on connection between send and reap