[issue #25] restauration de l'installation de ntp à la préparation de l'image

remplace timesyncd

config/read-only-fs.sh

 
 # Replace log management with busybox (use logread if needed)
 echo "Installing ntp and busybox-syslogd..."
-apt-get -y --force-yes install busybox-syslogd; dpkg --purge rsyslog
+apt-get -y --force-yes install ntp busybox-syslogd; dpkg --purge rsyslog
 
 echo "Configuring system..."