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/tests/gsm0408/gsm0408_test.c b/openbsc/tests/gsm0408/gsm0408_test.c
index 7acc93f..e81394f 100644
--- a/openbsc/tests/gsm0408/gsm0408_test.c
+++ b/openbsc/tests/gsm0408/gsm0408_test.c
@@ -122,7 +122,7 @@
 static inline void test_si2q_u(void)
 {
 	struct gsm_bts *bts;
-	struct gsm_network *network = gsm_network_init(1, 1, NULL);
+	struct gsm_network *network = gsm_network_init(tall_bsc_ctx, 1, 1, NULL);
 	printf("Testing SYSINFO_TYPE_2quater UARFCN generation:\n");
 
 	if (!network)
@@ -149,7 +149,7 @@
 static inline void test_si2q_e(void)
 {
 	struct gsm_bts *bts;
-	struct gsm_network *network = gsm_network_init(1, 1, NULL);
+	struct gsm_network *network = gsm_network_init(tall_bsc_ctx, 1, 1, NULL);
 	printf("Testing SYSINFO_TYPE_2quater EARFCN generation:\n");
 
 	if (!network)