Distinguish addresses in DHT persistence test

Uses loopback for the test DHT server, a local address provided
by the network-address module for the client. This is the pattern
used in other tests.

test/node/persist-dht-nodes.js

@@ -1,33 +1,35 @@
 var test = require('tape')
 var tmp = require('tmp')
 var fs = require('fs')
+var networkAddress = require('network-address')
 var DHT = require('bittorrent-dht/server')
 var WebTorrent = require('../../')
 
-var localHost = '127.0.0.1'
+var loopback = '127.0.0.1'
+var localAddress = networkAddress.ipv4()
 var port = 9999
 
-test('Save DHT state', function (t) {
+test.only('Save DHT state', function (t) {
   t.plan(4)
   var saveFile = tmp.tmpNameSync()
   var dhtServer = new DHT({ bootstrap: false })
   dhtServer.on('error', function (err) { t.fail(err) })
   dhtServer.on('warning', function (err) { t.fail(err) })
   dhtServer.listen(port, function handleServerListening () {
     var client = new WebTorrent({
-      dht: { bootstrap: false },
+      dht: { bootstrap: false, host: localAddress },
       dhtState: saveFile
     })
     client.on('error', function (err) { t.fail(err) })
     client.on('warning', function (err) { t.fail(err) })
-    client.dht.addNode({ host: localHost, port: port })
+    client.dht.addNode({ host: loopback, port: port })
     client.dht.on('node', function handleNodeAdded () {
       client.saveDhtState(function handleDhtStateSaved () {
         var dhtStateJson = fs.readFileSync(saveFile)
         var dhtState = JSON.parse(dhtStateJson)
         var nodes = dhtState.nodes
         var node = nodes[0]
-        t.equal(node.host, localHost)
+        t.equal(node.host, loopback)
         t.equal(node.port, port)
         client.destroy(function handleClientDestroyed (err) {
           t.error(err, 'client destroyed')