Simplify _recordsFor function

It appears that it previously allowed the name and type to be optional.
Since this is no longer the case, we can remove a lot of the logic from
the function body now

lib/mdns-server.js

@@ -90,21 +90,12 @@ Server.prototype._respondToQuery = function (query) {
 }
 
 Server.prototype._recordsFor = function (name, type) {
- var self = this
-
- type = type ? [type] : Object.keys(this.registry)
+ if (!(type in this.registry)) return []
 
- return flatten.depth(type.map(function (type) {
- if (!(type in self.registry)) return []
- if (name) {
- return self.registry[type].filter(function (record) {
- var _name = ~name.indexOf('.') ? record.name : record.name.split('.')[0]
- return dnsEqual(_name, name)
- })
- } else {
- return self.registry[type]
- }
- }), 1)
+ return this.registry[type].filter(function (record) {
+ var _name = ~name.indexOf('.') ? record.name : record.name.split('.')[0]
+ return dnsEqual(_name, name)
+ })
 }
 
 function isDuplicateRecord (a) {