dissolve libcommon: move talloc ctx into msc_main.c, drop talloc_ctx.c

Drop tall_bsc_ctx; in mncc_sock_init(), talloc the mncc_sock_state from
gsm_network.

In tests or utils, move from using an extern tall_bsc_ctx to a local root
context pointer.

Change-Id: I92c252be1d1e7634f1653de47d37c99d77d9501c
diff --git a/include/osmocom/msc/gsup_client.h b/include/osmocom/msc/gsup_client.h
index ce065a6..59e650f 100644
--- a/include/osmocom/msc/gsup_client.h
+++ b/include/osmocom/msc/gsup_client.h
@@ -54,7 +54,8 @@
 	int got_ipa_pong;
 };
 
-struct gsup_client *gsup_client_create(const char *unit_name,
+struct gsup_client *gsup_client_create(void *talloc_ctx,
+				       const char *unit_name,
 				       const char *ip_addr,
 				       unsigned int tcp_port,
 				       gsup_client_read_cb_t read_cb,