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/gprs/gprs_test.c b/tests/gprs/gprs_test.c
index 2dcbafa..99e3ea5 100644
--- a/tests/gprs/gprs_test.c
+++ b/tests/gprs/gprs_test.c
@@ -130,7 +130,8 @@
 
 int main(int argc, char **argv)
 {
-	osmo_init_logging(&info);
+	void *ctx = talloc_named_const(NULL, 0, "gprs_test");
+	osmo_init_logging2(ctx, &info);
 
 	test_8_4_2();
 	test_gprs_timer_enc_dec();