gsup_test: also check stderr

Configure logging to be deterministic and add stderr checking to testuite.at.

However, exclude the thousands of message modification log lines from the log
to not have a huge test expectation file.

Change-Id: I0dd7112967a64a168556b62e5ec15107b7608ffb
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 5731bf8..f6d4db3 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -177,7 +177,8 @@
 	     vty/vty_test.ok comp128/comp128_test.ok			\
 	     utils/utils_test.ok stats/stats_test.ok			\
 	     bitvec/bitvec_test.ok msgb/msgb_test.ok bits/bitcomp_test.ok \
-	     sim/sim_test.ok tlv/tlv_test.ok gsup/gsup_test.ok		\
+	     sim/sim_test.ok tlv/tlv_test.ok				\
+	     gsup/gsup_test.ok gsup/gsup_test.err			\
 	     oap/oap_test.ok fsm/fsm_test.ok fsm/fsm_test.err		\
 	     write_queue/wqueue_test.ok socket/socket_test.ok		\
 	     socket/socket_test.err