Add NTP server to Undercloud for offline deployments

Add an NTP server to the Undercloud for optional use with the Overcloud. This allows for a default NTP server pointing at the Undercloud, and allows for offline deployments without Internet access or access to an external NTP server. An external NTP server may still be used in production, but this simplifies proof-of-concept deployments and removes a dependency for CI or test deployments.

Note that since this blueprint was registered, tripleo-quickstart added support for setting up an NTP server on the Undercloud. We may be able to reuse that code, or we may decide that since this feature will be delivered in oooq that we don't need it in the undercloud setup scripts.