test: fix test-net-dns-custom-lookup test assertion

The assertion made an assumption that the IPv6 address would always be
`::1`. Since the address can be different on different platforms, it
has been changed to allow multiple addresses.

test/parallel/test-net-dns-custom-lookup.js

@@ -4,6 +4,12 @@ var net = require('net');
 var dns = require('dns');
 var ok = false;
 
+var addrCandidates = [ common.localhostIPv4 ];
+if (common.hasIPv6) {
+  addrCandidates.push('::ffff:127.0.0.1');
+  addrCandidates.push('::1');
+}
+
 function check(addressType, cb) {
   var server = net.createServer(function(client) {
     client.end();
@@ -12,14 +18,16 @@ function check(addressType, cb) {
   });
 
   var address = addressType === 4 ? '127.0.0.1' : '::1';
+  var host = addressType === 4 ? 'localhost' : 'ip6-localhost';
   server.listen(common.PORT, address, function() {
     net.connect({
       port: common.PORT,
-      host: 'localhost',
+      hostname: host,
+      family: addressType,
       lookup: lookup
     }).on('lookup', function(err, ip, type) {
       assert.equal(err, null);
-      assert.equal(ip, address);
+      assert.notEqual(-1, addrCandidates.indexOf(ip), ip + ' exists');
       assert.equal(type, addressType);
       ok = true;
     });