test-lib: enable MALLOC_* for the actual tests

1b3185f (MALLOC_CHECK: various clean-ups, 2012-09-14) moved around the
MALLOC_CHECK_ and MALLOC_PERTURB_ assignments, intending to limit
their effect to only the test runs.  However, they were actually
enabled only during test cleanup.  Call setup/teardown_malloc_check
also around the evaluation of the actual test snippet.

Signed-off-by: Thomas Rast <trast@inf.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/test-lib.sh

@@ -337,8 +337,10 @@ test_eval_ () {
 test_run_ () {
 	test_cleanup=:
 	expecting_failure=$2
+	setup_malloc_check
 	test_eval_ "$1"
 	eval_ret=$?
+	teardown_malloc_check
 
 	if test -z "$immediate" || test $eval_ret = 0 || test -n "$expecting_failure"
 	then