Restore the state of INNODB_THREAD_CONCURRENCY to silence this warning:

  TEST                                      RESULT   TIME (ms)
  ------------------------------------------------------------
  
  worker[1] Using MTR_BUILD_THREAD 250, with reserved ports 12500..12509
  main.innodb                              [ pass ]   8803
  
  MTR's internal check of the test case 'main.innodb' failed.
  This means that the test case does not preserve the state that existed
  before the test case was executed.  Most likely the test case did not
  do a proper clean-up.
  This is the diff of the states of the servers before and after the
  test case was executed:
  mysqltest: Logging to '/tmp/autotest.sh-20090330_033000-5.1.5Hg8CY/mysql-5.1/mysql-test/var/tmp/check-mysqld_1.log'.
  mysqltest: Results saved in '/tmp/autotest.sh-20090330_033000-5.1.5Hg8CY/mysql-5.1/mysql-test/var/tmp/check-mysqld_1.result'.
  mysqltest: Connecting to server localhost:12500 (socket /tmp/autotest.sh-20090330_033000-5.1.5Hg8CY/mysql-5.1/mysql-test/var/tmp/mysqld.1.sock) as 'root', connection 'default', attempt 0 ...
  mysqltest: ... Connected.
  mysqltest: Start processing test commands from './include/check-testcase.test' ...
  mysqltest: ... Done processing test commands.
  --- /tmp/autotest.sh-20090330_033000-5.1.5Hg8CY/mysql-5.1/mysql-test/var/tmp/check-mysqld_1.result	2009-03-30 14:12:31.000000000 +0300
  +++ /tmp/autotest.sh-20090330_033000-5.1.5Hg8CY/mysql-5.1/mysql-test/var/tmp/check-mysqld_1.reject	2009-03-30 14:12:41.000000000 +0300
  @@ -99,7 +99,7 @@
   INNODB_SUPPORT_XA	ON
   INNODB_SYNC_SPIN_LOOPS	20
   INNODB_TABLE_LOCKS	ON
  -INNODB_THREAD_CONCURRENCY	8
  +INNODB_THREAD_CONCURRENCY	16
   INNODB_THREAD_SLEEP_DELAY	10000
   INSERT_ID	0
   INTERACTIVE_TIMEOUT	28800
  
  mysqltest: Result content mismatch
  
  not ok