Make sure the clone service doesn't cache the location

The default clone path might be changed in the VS Git settings, so make
sure the clone service picks those changes up (which are read in the
ctor) by not caching the service itself.

Author: shana

src/GitHub.App/Services/RepositoryCloneService.cs

@@ -15,7 +15,7 @@ namespace GitHub.Services
     /// by Team Explorer.
     /// </summary>
     [Export(typeof(IRepositoryCloneService))]
-    [PartCreationPolicy(CreationPolicy.Shared)]
+    [PartCreationPolicy(CreationPolicy.NonShared)]
     public class RepositoryCloneService : IRepositoryCloneService
     {
         static readonly Logger log = LogManager.GetCurrentClassLogger();