Split DNS database handling into its own recipe.

Make the other recipes attribute-driven while we are at it.
The method that the DNS database role is using to keep the database updated
is racy right now, that raciness will be resolved by updating how we
manage node role runs.
Merge pull request #61 from VictorLowther/pull-req-master-763d805705b2c4a304d3ae9606be913bd4cca504

https://github.com/crowbar/barclamp-dns/pull/61

Merged by devtool for cloudedge