Allow forwarding  reverse DNS queries for the default local zones. 

Unbound by default won't forward reverse dns queries for the default  zones (localhost, reverse 127.0.0.1 and ::1, and the AS112 zones)

This change allows us to override the default zones ending with something like

server:
  local-zone: "10.in-addr.arpa." nodefault
forward-zone:
  name: "10.in-addr.arpa"
  forward-addr: xxxx