perf tests: Add a testcase for histogram output sorting

With new output fields option, its internal implementation was changed
so add a new testcase to verify whether it breaks things.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/1400480762-22852-21-git-send-email-namhyung@kernel.org
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
diff --git a/tools/perf/tests/hists_link.c b/tools/perf/tests/hists_link.c
index 4e783db..5ffa2c3 100644
--- a/tools/perf/tests/hists_link.c
+++ b/tools/perf/tests/hists_link.c
@@ -332,6 +332,7 @@
 out:
 	/* tear down everything */
 	perf_evlist__delete(evlist);
+	reset_output_field();
 	machines__exit(&machines);
 
 	return err;