db: Remove the struct gsm_network from the database layer

The database code should not know about the network. Move the
setting of the network pointer into the subscriber layer.
diff --git a/openbsc/src/libmsc/vty_interface_layer3.c b/openbsc/src/libmsc/vty_interface_layer3.c
index acb4af7..e0324d6 100644
--- a/openbsc/src/libmsc/vty_interface_layer3.c
+++ b/openbsc/src/libmsc/vty_interface_layer3.c
@@ -229,7 +229,7 @@
 	struct gsm_network *gsmnet = gsmnet_from_vty(vty);
 	struct gsm_subscriber *subscr;
 
-	subscr = db_create_subscriber(gsmnet, argv[0]);
+	subscr = subscr_create_subscriber(gsmnet, argv[0]);
 	if (!subscr) {
 		vty_out(vty, "%% No subscriber created for IMSI %s%s",
 			argv[0], VTY_NEWLINE);