use osmo_init_logging2(), fix regression test memleaks

Particularly gbproxy_test.c had various mem leaks, which (will) show up with
gcc (Debian 7.3.0-15) 7.3.0 address sanitizer. Fix those leaks to verify that
we don't have memleaks in the production code.

Change-Id: Ia4204c8b3d895b42c103edecb61b99d3d22bd36f
diff --git a/tests/slhc/slhc_test.c b/tests/slhc/slhc_test.c
index bb0e26c..5c13313 100644
--- a/tests/slhc/slhc_test.c
+++ b/tests/slhc/slhc_test.c
@@ -250,17 +250,20 @@
 int main(int argc, char **argv)
 {
 	void *ctx;
-
-	osmo_init_logging(&info);
+	void *log_ctx;
 
 	ctx = talloc_named_const(NULL, 0, "slhc_ctx");
+	log_ctx = talloc_named_const(ctx, 0, "log");
+	osmo_init_logging2(log_ctx, &info);
 
 	test_slhc(ctx);
 
 	printf("Done\n");
 
 	talloc_report_full(ctx, stderr);
+	talloc_free(log_ctx);
 	OSMO_ASSERT(talloc_total_blocks(ctx) == 1);
+	talloc_free(ctx);
 	return 0;
 }