Make $ntp_servers optional as it should be
Make $ntp_servers optional as it should be

When data types were added the $ntp_servers parameter was accidentally made
mandatory, even though use of $ntp_pools is a valid alternative.

Signed-off-by: Samuli Seppänen <34cd69fd1edf1dbeb60d8f1ed9a92a19d78eb447@gmail.com>

Puppet-Finland/ntp