[IMP] point_of_sale: migrate the script that sets the rpi leds

When the server is answering HTTP requests, the status led (green one)
of the Raspberry Pi will turn on. Contrary to the previous script this
will not exit and keep running every 5 seconds. This way we can easily
troubleshoot connection issues (if led is on and we can't connect it's a
network issue, otherwise it's an issue with Odoo).

addons/point_of_sale/tools/posbox/overwrite_after_init/etc/rc.local

@@ -20,4 +20,6 @@ fi
 mkdir -p /var/run/odoo
 chown pi:pi /var/run/odoo
 
+/home/pi/led_status.sh &
+
 exit 0

addons/point_of_sale/tools/posbox/overwrite_before_init/home/pi/led_status.sh

@@ -0,0 +1,19 @@
+#!/usr/bin/env bash
+
+set_brightness() {
+    echo "${1}" > /sys/class/leds/led0/brightness
+}
+
+check_status_loop() {
+    while true ; do
+	if wget --quiet localhost:8069/hw_proxy/hello -O /dev/null ; then
+	    set_brightness 255
+	else
+	    set_brightness 0
+	fi
+        sleep 5
+    done
+}
+
+echo none > /sys/class/leds/led0/trigger
+check_status_loop