tests/sms_queue: track the use of NULL talloc memory contexts

As we don't initialize all talloc contects of libmsc, let's make
sure that there is nothing left in the NULL context after the
unit test execution is finished.

Change-Id: I99fd82750aff376e4d90eaa2402ec41f4d59ef86
diff --git a/tests/sms_queue/sms_queue_test.c b/tests/sms_queue/sms_queue_test.c
index f64f715..84ca6b5 100644
--- a/tests/sms_queue/sms_queue_test.c
+++ b/tests/sms_queue/sms_queue_test.c
@@ -220,6 +220,9 @@
 	void *msgb_ctx;
 	void *logging_ctx;
 
+	/* Track the use of talloc NULL memory contexts */
+	talloc_enable_null_tracking();
+
 	talloc_ctx = talloc_named_const(NULL, 0, "sms_queue_test");
 	msgb_ctx = msgb_talloc_ctx_init(talloc_ctx, 0);
 	logging_ctx = talloc_named_const(talloc_ctx, 0, "logging");
@@ -258,6 +261,9 @@
 	OSMO_ASSERT(talloc_total_size(talloc_ctx) == 0);
 	talloc_free(talloc_ctx);
 
+	talloc_report_full(NULL, stderr);
+	talloc_disable_null_tracking();
+
 	return 0;
 }