Fixes #272

On my system I found that 4 seconds was not logn enough for DHT to start.
Time for a new computer perhaps...

Anyway I have bumped the timeout to 10 seconds (FYI: my system on average took
6 seconds to start DHT).

I have also added in a check to see if the timeout has indeed been reached.

src/OmniSharp/Dnx/DesignTimeHostManager.cs

@@ -63,7 +63,7 @@ public void Start(string hostId, Action<int> onConnected)
                 using (var socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp))
                 {
                     var t1 = DateTime.UtcNow;
-                    var dthTimeout = TimeSpan.FromSeconds(4);
+                    var dthTimeout = TimeSpan.FromSeconds(10);
                     while (!socket.Connected && DateTime.UtcNow - t1 < dthTimeout)
                     {
                         Thread.Sleep(500);
@@ -76,6 +76,13 @@ public void Start(string hostId, Action<int> onConnected)
                             // this happens when the DTH isn't listening yet
                         }
                     }
+
+                    if (!socket.Connected)
+                    {
+                        // reached timeout
+                        _logger.LogError("Failed to launch DesignTimeHost in a timely fashion.");
+                        return;
+                    }
                 }
 
                 if (_designTimeHostProcess.HasExited)
@@ -98,7 +105,7 @@ public void Start(string hostId, Action<int> onConnected)
                 onConnected(port);
             }
         }
-        
+
         public void Stop()
         {
             lock (_processLock)