Make host management optional
Make host management optional

If a site is managing their own hosts file,
it may be desirable to remove the current hosts
management. This patch makes hosts management
optional by removing the required parameters
and only setting /etc/hosts if they are set.

michaeltchapman/puppet-stacktira,michaeltchapman/puppet-stacktira,michaeltchapman/puppet-openstacklib,michaeltchapman/puppet-openstacklib