utils_test: check stderr to catch sanitizer issues

Recent OS#3407 shows that we should verify stderr to catch sanitizer failures.
(They might not always be ignorable like that one.)

Change-Id: Ic9e437a1cc96ae081e0fd6a9b6e3156987e14c0c
diff --git a/tests/testsuite.at b/tests/testsuite.at
index 15a89b6..43b58e8 100644
--- a/tests/testsuite.at
+++ b/tests/testsuite.at
@@ -205,7 +205,8 @@
 AT_SETUP([utils])
 AT_KEYWORDS([utils])
 cat $abs_srcdir/utils/utils_test.ok > expout
-AT_CHECK([$abs_top_builddir/tests/utils/utils_test], [0], [expout], [ignore])
+cat $abs_srcdir/utils/utils_test.err > experr
+AT_CHECK([$abs_top_builddir/tests/utils/utils_test], [0], [expout], [experr])
 AT_CLEANUP
 
 AT_SETUP([stats])