[tests] Ensure tests don't hit upnp port forwarding

These are short running tests, so don't bother init'ing
port forwarding support or DHT.

src/Tests/Tests.MonoTorrent.IntegrationTests/IntegrationTests.cs

@@ -174,6 +174,8 @@ private ClientEngine GetEngine (int port)
                 ReportedAddress = new IPEndPoint (IPAddress.Parse ("127.0.0.1"), port),
                 AutoSaveLoadFastResume = false,
                 CacheDirectory = _directory.FullName,
+                DhtEndPoint = null,
+                AllowPortForwarding = false,
             };
             var engine = new ClientEngine (settingBuilder.ToSettings ());
             return engine;