tests/stats: enable logging in test output

Move test output from stdout to stderr and enable logging to stderr.
This is in preparation for the next patch, which will add a new log
message when osmo_stat_item_get_next() skips a value.

Related: SYS#4877
Change-Id: Ie0eaec2f93ac6859397a6bfca45039fdcc27cb9e
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 158bc69..0f587ce 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -368,7 +368,8 @@
 	     vty/ok_tabs.cfg \
 	     vty/ok_deprecated_logging.cfg \
 	     comp128/comp128_test.ok bits/bitfield_test.ok		\
-	     utils/utils_test.ok utils/utils_test.err stats/stats_test.ok \
+	     utils/utils_test.ok utils/utils_test.err 			\
+	     stats/stats_test.ok stats/stats_test.err			\
 	     bitvec/bitvec_test.ok msgb/msgb_test.ok bits/bitcomp_test.ok \
 	     sim/sim_test.ok tlv/tlv_test.ok abis/abis_test.ok		\
 	     gsup/gsup_test.ok gsup/gsup_test.err			\