pihole.log permissions

This change makes pihole more friendly to the non-existence of the pihole.log file. This can help with systems that are configured to mount /var/log as a tmpfs volume. It may also help with systems where the pihole.log file is accidentally/unintentionally removed. 

Further discussion around the details of this change are in https://github.com/pi-hole/pi-hole/issues/1798

advanced/pihole-FTL.service

@@ -25,9 +25,9 @@ start() {
   if is_running; then
     echo "pihole-FTL is already running"
   else
-    touch /var/log/pihole-FTL.log /run/pihole-FTL.pid /run/pihole-FTL.port
+    touch /var/log/pihole-FTL.log /run/pihole-FTL.pid /run/pihole-FTL.port /var/log/pihole.log
     chown pihole:pihole /var/log/pihole-FTL.log /run/pihole-FTL.pid /run/pihole-FTL.port /etc/pihole
-    chmod 0644 /var/log/pihole-FTL.log /run/pihole-FTL.pid /run/pihole-FTL.port
+    chmod 0644 /var/log/pihole-FTL.log /run/pihole-FTL.pid /run/pihole-FTL.port /var/log/pihole.log
     su -s /bin/sh -c "/usr/bin/pihole-FTL" "$FTLUSER"
     echo
   fi