Use TESTS_BINDIR to point out bin dir for "client_test"
mysql-test-run.sh:
  Export TESTS_BINDIR to be used from --exec


mysql-test/mysql-test-run.sh:
  Export TESTS_BINDIR to be used from --exec
mysql-test/t/client_test.test:
  Use TESTS_BINDIR to point out bin dir for "client_test"