use osmo_init_logging2() with proper talloc ctx

Ironically, when deprecating osmo_init_logging() in
I216837780e9405fdaec8059c63d10699c695b360, I forgot to change the callers
within libosmocore itself, i.e. in the various regression tests.

Change-Id: Ia36c248f99353d5baaa2533f46a2f60a8579bdf8
diff --git a/tests/oap/oap_test.c b/tests/oap/oap_test.c
index dea5c11..32676ca 100644
--- a/tests/oap/oap_test.c
+++ b/tests/oap/oap_test.c
@@ -173,7 +173,9 @@
 
 int main(int argc, char **argv)
 {
-	osmo_init_logging(&info);
+	void *ctx = talloc_named_const(NULL, 0, "oap_test");
+	osmo_init_logging2(ctx, &info);
+	msgb_talloc_ctx_init(ctx, 0);
 
 	test_oap_messages_dec_enc();