Add warnings and safety checks and documentation

The changes in the `redhat-default-zones` branch, when released, may cause
upgrade difficulties for Red Hat system administrators. Try to ease the
transition.

data/common.yaml

@@ -2,6 +2,7 @@
 bind::defaults::supported: false
 bind::defaults::random_device: '/dev/random'
 bind::defaults::rndc: true
+bind::defaults::default_zones_warning: false
 
 bind::forwarders: ''
 bind::dnssec: true

data/osfamily/RedHat.yaml

@@ -9,5 +9,6 @@ bind::defaults::managed_keys_directory: '/var/named/dynamic'
 bind::defaults::confdir: '/etc/named'
 bind::defaults::namedconf: '/etc/named.conf'
 bind::defaults::cachedir: '/var/named'
+bind::defaults::default_zones_warning: true
 
 bind::updater::keydir: '/etc/named/keys'