Fix subunit-trace output with tempest run

Now that we're using tempest run in tox it became clear that the
subunit-trace arguments we were using in tempest run did not match what
we were previously using in pretty_tox.sh. This makes debugging failures
slightly more difficult than before because the failures aren't printed
at the end of the run. This commit adds the necessary flags to tempest
run calling of subunit-trace to have the same behavior as before.

Change-Id: Ib066acca792d4f357763235ef4593062e9978f0b
diff --git a/tempest/cmd/run.py b/tempest/cmd/run.py
index fef836c..236953c 100644
--- a/tempest/cmd/run.py
+++ b/tempest/cmd/run.py
@@ -264,8 +264,8 @@
 
             run_thread = threading.Thread(target=run_argv_thread)
             run_thread.start()
-            returncodes['subunit-trace'] = subunit_trace.trace(subunit_r,
-                                                               sys.stdout)
+            returncodes['subunit-trace'] = subunit_trace.trace(
+                subunit_r, sys.stdout, post_fails=True, print_failures=True)
             run_thread.join()
             subunit_r.close()
             # python version of pipefail