Add test for virtual machines and local clocks

This commit provides a spec test for pull request #49 and commit
01273c53f1cf2015c3ff5a9f704828225d900e03 which specifies that virtual
machines should not use the local clock. This test attempts to protect
against a regression on that statement.
User @servers_real instead of servers_real to avoid warnings
Add ntp::config, a class to manage the ntp configuration file.
Add ntp::install, a class to manage the ntp packages.
Add ntp::params, a place to centralize all configuration information.
Refactor out the main ntp class to break it up into 4 smaller ones.
Add ntp::service, a class to manage the ntp service.
Rename all the servers_real functions to servers.
Rework specs to pass with renamed params.