openssh: Make sure SFTP is working.

If sftp-server is installed, use it.

net/openssh/files/sshd.init

@@ -285,6 +285,8 @@ set_params()
 	set_password_auth "${PasswordAuth}"
 	set_root_login "${RootLogin}" "${RootPasswordAuth}"
 
+	append_config "Subsystem" "sftp /usr/lib/sftp-server"
+
 	# finalize
 	mkdir -p "$(dirname "${ConfigFile}")"
 	mv "${TEMPCONF}" "${ConfigFile}"