[FIX] point_of_sale: make POSBox print only one ticket when losing wifi

The POSBox attempts to maintain whatever Wi-Fi connection it has as best
it can. When it loses it's current Wi-Fi connection it will attempt
to recreate it every 30 seconds. This works well, but a side-effect of
this is that it'll also print a 'Could not connect to LAN' ticket every
time it fails. If you where to leave the POSBox with Wi-Fi on for an
extended period of time you could return to a lot of 'Could not connect
to LAN' tickets.

This makes it so that the 'Could not connect to LAN' ticket only gets
printed once upon connection loss. Although it would be simpler to just
not print this ticket at all when losing connection, it is very useful
to know when the POSBox has lost connection. Otherwise when it loses
connection it would stop working and noone would know why.

addons/point_of_sale/tools/posbox/configuration/connect_to_wifi.sh

@@ -7,6 +7,7 @@ function connect () {
 	WPA_PASS_FILE="/tmp/wpa_pass.txt"
 	PERSISTENT_WIFI_NETWORK_FILE="/home/pi/wifi_network.txt"
 	CURRENT_WIFI_NETWORK_FILE="/tmp/current_wifi_network.txt" # used to repair connection when we lose it
+	LOST_WIFI_FILE="/tmp/lost_wifi.txt"
 	ESSID="${1}"
 	PASSWORD="${2}"
 	PERSIST="${3}"
@@ -15,6 +16,7 @@ function connect () {
 	sleep 3
 
 	sudo pkill -f keep_wifi_alive.sh
+	WIFI_WAS_LOST=$?
 
 	# make network choice persistent
 	if [ -n "${ESSID}" ] ; then
@@ -54,13 +56,24 @@ function connect () {
 
 	# give dhcp some time
 	timeout 30 sh -c 'until ifconfig wlan0 | grep "inet addr:" ; do sleep 0.1 ; done'
+	TIMEOUT_RETURN=$?
 
-	if [ $? -eq 124 ] && [ -z "${NO_AP}" ] ; then
+	if [ ${TIMEOUT_RETURN} -eq 124 ] && [ -z "${NO_AP}" ] ; then
 		logger -t posbox_connect_to_wifi "Failed to connect, forcing Posbox AP"
 		sudo /home/pi/odoo/addons/point_of_sale/tools/posbox/configuration/wireless_ap.sh "force" &
 	else
-		logger -t posbox_connect_to_wifi "Restarting odoo"
-		sudo service odoo restart
+		if [ ${TIMEOUT_RETURN} -ne 124 ] ; then
+			rm -f "${LOST_WIFI_FILE}"
+		fi
+
+		if [ ! -f "${LOST_WIFI_FILE}" ] ; then
+			logger -t posbox_connect_to_wifi "Restarting odoo"
+			sudo service odoo restart
+		fi
+
+		if [ ${WIFI_WAS_LOST} -eq 0 ] ; then
+			touch "${LOST_WIFI_FILE}"
+		fi
 
 		logger -t posbox_connect_to_wifi "Starting wifi keep alive script"
 		/home/pi/odoo/addons/point_of_sale/tools/posbox/configuration/keep_wifi_alive.sh &