NTP_Sync doesn't work when several ntp servers are set

[Mathieu Parent]

If several ntp servers are set, file /etc/puppi/checks/20-NTP_Sync will look like this:

/usr/lib/nagios/plugins/check_ntp -H 0.debian.pool.ntp.org1.debian.pool.ntp.org2.debian.pool.ntp.org3.debian.pool.ntp.org

(i.e. : servers are concatenated)