This way, a crash of mysqltest will be visible in the test logs
(output of mysql-test-run).


mysql-test/mysql-test-run.sh:
  by design mysqltest returns 0 or 1 or 2 (see the exit()s and the return()
  of main()). So any greater code is a crash, I guess.
  On build and on my machine, 139 is segfault and 134 is assertion failure.