Create /etc/hosts in production

[matze]

Our production servers do perform DNS lookups when communicating with each other. We can avoid this (and all implications) by using the /etc/hosts generating mechanism in production as well.

What to change

Extend the infrastructure repository, namely it's base module, so that the /etc/hosts file is not only created in development but also in production (based on the environment's hiera data).

[matze]

Note that this ticket depends on #1568 - we won't roll-out the modifications here before we've set up proper Nagios tests for our DNS records.

[matze]

While this has been implemented in the context of the Hiera migration, one should note that using more sophisticated DNS infrastructure may not only render this feature obsolete but also cause it being considered maintenance overhead.