drd/tests/pth_barrier[23]: Filter output such that only the error count is kept

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@11940 a5019735-40e9-0310-863c-91ae7b9d1cf9
diff --git a/drd/tests/pth_barrier2.vgtest b/drd/tests/pth_barrier2.vgtest
index 1fe9408..56a897b 100644
--- a/drd/tests/pth_barrier2.vgtest
+++ b/drd/tests/pth_barrier2.vgtest
@@ -1,4 +1,4 @@
 prereq: test -e pth_barrier && ./supported_libpthread
 prog: pth_barrier
 args: 2 32 1
-stderr_filter: filter_error_summary
+stderr_filter: filter_error_count