Resolve deprecation warning from NTP module

Some time back the folks at Puppet Labs deprecated the autoupdate
parameter to the NTP module.  However puppet-coi still invokes
it, which causes a deprecation warning to be emitted:

Notice: Scope(Class[Ntp]): autoupdate parameter has been deprecated
  and replaced with package_ensure.  Set this to latest for the
  same behavior as autoupdate => true.

This patch corrects the parameter we feed to the NTP module to
remove the deprecation warning.

Partial-Bug: #1281896