main, tests: use msgb_talloc_ctx_init() (new)

msgb_set_talloc_ctx() is deprecated since libosmocore commit
f45334be29016a36594aacc07c90e262e4994525 / change-id
I747fbbf977c4d2c868c8dead64cfc5fd86eb8d4c

Change-Id: I8d40abec428b739460ed545c9983d1b63021bd08
diff --git a/tests/ms/MsTest.cpp b/tests/ms/MsTest.cpp
index 0930354..d66f578 100644
--- a/tests/ms/MsTest.cpp
+++ b/tests/ms/MsTest.cpp
@@ -538,7 +538,7 @@
 	if (!tall_pcu_ctx)
 		abort();
 
-	msgb_set_talloc_ctx(tall_pcu_ctx);
+	msgb_talloc_ctx_init(tall_pcu_ctx, 0);
 	osmo_init_logging(&debug_log_info);
 	log_set_use_color(osmo_stderr_target, 0);
 	log_set_print_filename(osmo_stderr_target, 0);