gluon-setup-mode: always finalize the overlay before rebooting

When an early reboot is triggered because an upgrade script has disabled the
config mode, we need to explicitly call /etc/init.d/done, otherwise the overlay
will not be finalized after a firstboot and we get an endless reboot loop.

gluon/gluon-setup-mode/files/lib/gluon/setup-mode/rc.d/S15gluon-setup-mode

@@ -15,6 +15,7 @@ boot() {
 	else
 		# This can happen after an upgrade from a version before the config file was called gluon-setup-mode
 		# We'll just reboot to return to the normal mode...
+		/etc/init.d/done boot
 		reboot
 	fi
 }