A follow-up commit will save the domain name on the request object but
we can't call that property 'domain' because that gets intercepted by
src/node.cc and lib/domain.js to implement the node.js feature of the
same name.
To avoid confusion, rename all variables called 'domain' to 'hostname'.
getServers returns an array of ips that are currently being used for
resolution
setServers takes an array of ips that are to be used for resolution,
this will throw if there's invalid input but preserve the original
configuration
