fix #2071 ObjectDatabase.Write<T>(Stream, long) does not respect T

LibGit2Sharp/ObjectDatabase.cs

@@ -202,7 +202,7 @@ public virtual ObjectId Write<T>(Stream stream, long numberOfBytesToConsume) whe
                 throw new ArgumentException("The stream cannot be read from.", "stream");
             }
 
-            using (var odbStream = Proxy.git_odb_open_wstream(handle, numberOfBytesToConsume, GitObjectType.Blob))
+            using (var odbStream = Proxy.git_odb_open_wstream(handle, numberOfBytesToConsume, GitObject.TypeToKindMap[typeof(T)]))
             {
                 var buffer = new byte[4 * 1024];
                 long totalRead = 0;