Make waitForDns provider specific

This will allow us to create a proper 'noop' backend that does
not wait for dns to be in sync. This is required for local/intranet
setups.

src/dns/noop.js

@@ -4,7 +4,8 @@ exports = module.exports = {
     upsert: upsert,
     get: get,
     del: del,
-    getChangeStatus: getChangeStatus
+    getChangeStatus: getChangeStatus,
+    waitForDns: require('./waitfordns.js')
 };
 
 var assert = require('assert'),