mscsplit: gsm_network_init(): add explicit root talloc ctx

Decouple the root talloc context from libbsc's global talloc_bsc_ctx.

This allows to define the root talloc ctx from a main() scope, which in turn
helps decouple libmsc from libbsc.

Change-Id: I92f6b47b1eeea2e8f3fba66f25d7e708e5659f8a
diff --git a/openbsc/src/utils/bs11_config.c b/openbsc/src/utils/bs11_config.c
index 3fb74bf..227b9f8 100644
--- a/openbsc/src/utils/bs11_config.c
+++ b/openbsc/src/utils/bs11_config.c
@@ -894,7 +894,7 @@
 	handle_options(argc, argv);
 	bts_model_bs11_init();
 
-	gsmnet = gsm_network_init(1, 1, NULL);
+	gsmnet = gsm_network_init(tall_bs11cfg_ctx, 1, 1, NULL);
 	if (!gsmnet) {
 		fprintf(stderr, "Unable to allocate gsm network\n");
 		exit(1);