tests: sanitize: fix mem leaks, clean after tests

Fix various mem leaks in the testing code.

Add test_common_cleanup() in test_common.c, to free talloc contexts; call in
test-{helpers,hnbap,ranap}.c. Upon talloc ctx cleanup, ensure that they are
actually empty, in order to catch newly introduced mem leaks.

If non-empty, print talloc context reports.

Change-Id: Ic66c005f2a264774e18bb54e58b87bef5944511c
diff --git a/src/tests/test-ranap.c b/src/tests/test-ranap.c
index c1c7003..05be874 100644
--- a/src/tests/test-ranap.c
+++ b/src/tests/test-ranap.c
@@ -197,6 +197,8 @@
 	talloc_report(talloc_asn1_ctx, stdout);
 	talloc_report(tall_msgb_ctx, stdout);
 	//talloc_report(NULL, stdout);
+
+	test_common_cleanup();
 	printf("exit\n");
 	exit(0);
 }