The server shutdown and start code triggered the valgrind failures 
within nptl_pthread_exit_hack_handler on Ubuntu 9.04, x86 (but not amd64) 
in rpl_trigger.test file.

For fixing the bug, suppress valgrind failures within nptl_pthread_exit_hack_handler 
on Ubuntu 9.04, x86 (but not amd64). Because the server shutdown and start
code has been heavily used in mysql test set.

mysql-test/valgrind.supp:
  Add code for suppressing valgrind failures within nptl_pthread_exit_hack_handler on Ubuntu 9.04, x86 (but not amd64).