Rewrite the if so it works correctly

My last edit of this file caused issue even if /etc/timezone existed it wouldn't use the timezone value of it, the only file i would try to get the timezone out of is /etc/localtime.

generate_config.sh

@@ -16,7 +16,12 @@ if [ -z "$MAILCOW_HOSTNAME" ]; then
   read -p "Hostname (FQDN): " -ei "mx.example.org" MAILCOW_HOSTNAME
 fi
 
-[[ -a /etc/timezone ]] && TZ=$(cat /etc/timezone) || [[ -a /etc/localtime ]] && TZ=$(readlink /etc/localtime|sed -n 's|^.*zoneinfo/||p')
+if [[ -a /etc/timezone ]]; then 
+ TZ=$(cat /etc/timezone) 
+elif  [[ -a /etc/localtime ]]; then
+ TZ=$(readlink /etc/localtime|sed -n 's|^.*zoneinfo/||p')
+fi
+
 if [ -z "$TZ" ]; then
   read -p "Timezone: " -ei "Europe/Berlin" TZ
 else