adjust talloc context

there is no obvious reason why the endpoints that belong to a trunk would
have the (global) config as parent context, you can't really have endpoints
without a trunk anyway.

Change-Id: Id3d5fefc12b7d442c09c507b3a8b0231e46e3068

src/libosmo-mgcp/mgcp_trunk.c

@@ -123,7 +123,7 @@ int mgcp_trunk_alloc_endpts(struct mgcp_trunk *trunk)
 	OSMO_ASSERT(number_endpoints < 65534);
 
 	/* allocate pointer array for the endpoints */
-	trunk->endpoints = talloc_zero_array(trunk->cfg, struct mgcp_endpoint*,
+	trunk->endpoints = talloc_zero_array(trunk, struct mgcp_endpoint*,
 					     number_endpoints);
 	if (!trunk->endpoints)
 		return -1;