s3:rpc_server: let get_servers() callback of rpc_worker_main() return NTSTATUS

This means the rpc_worker_main() logic is the only layer that
needs to call exit() and its able to do some cleanup before.

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>

source3/rpc_server/rpc_worker.h

@@ -30,9 +30,10 @@ int rpc_worker_main(
 	size_t (*get_interfaces)(
 		const struct ndr_interface_table ***ifaces,
 		void *private_data),
-	size_t (*get_servers)(
+	NTSTATUS (*get_servers)(
 		struct dcesrv_context *dce_ctx,
 		const struct dcesrv_endpoint_server ***ep_servers,
+		size_t *num_ep_servers,
 		void *private_data),
 	void *private_data);