Unmanaged dns dnsproxy

Hello,

Those small modification will allow people to use their own dns puppet module, which may be a bit more comfortable than having to migrate their stuff to the puppet-dns used as dependency.

I've tested it, the smart-proxy is configured as expected, and foreman can catch it and interact with it. The only big difference is the zone is managed by some other puppet module (puppet-bind).

Cheers,

C. Jeanneret