desginate: simplify sample pool

in crowbar's world the dns-master is the master of all and slaves
forward all queries to dns-master. Under such a configuration there is
no need to query other nameservers as they still forward the query to
dns-master. So designate can just verify on one nameserver(dns-master)
and dns-master will take care of passing that info to all slaves.

Same goes for also_notifies: dns-master will notify all slaves in case
of either zone or recordset is updated/deleted.

this also further simplifies the designate pool config reducing  the
time required to create zone and recordsets.

This change is not really required but only eases out the config from
an admin perspective.

Also having multiple nameservers confuses designate in some cases as
according to these nameserver designate is not authoritative of some
zones and recordsets.

chef/cookbooks/designate/recipes/mdns.rb

@@ -20,8 +20,6 @@
 
 dns = node_search_with_cache("roles:dns-server").first
 dnsmaster = dns[:dns][:master_ip]
-dnsslaves = dns[:dns][:slave_ips].to_a
-dnsservers = [dnsmaster] + dnsslaves
 
 network_settings = DesignateHelper.network_settings(node)
 
@@ -36,12 +34,12 @@
 # non-hardcoded is high enough
 pools = [{
   "name" => "default-bind",
-  "description" => "Default BIND9 Pool",
+  "description" => "Sample Pool for designate (relies only 1 dns-master)",
   "id" => "794ccc2c-d751-44fe-b57f-8894c9f5c842",
   "attributes" => {},
   "ns_records" => [{ "hostname" => "#{dns[:fqdn]}.", "priority" => 1 }],
-  "nameservers" => dnsservers.map { |ip| { "host" => ip, "port" => 53 } },
-  "also_notifies" => dnsslaves.map { |ip| { "host" => ip, "port" => 53 } },
+  "nameservers" => [{ "host" => dnsmaster, "port" => 53 }],
+  "also_notifies" => [],
   "targets" => [{
     "type" => "bind9",
     "description" => "BIND9 Server 1",