Revert "make handles to be thread-local"

This reverts commit 0720ba5.

Author: colesbury

torch/csrc/cudnn/Handles.cpp

@@ -21,7 +21,7 @@ struct Handle {
 };
 
 std::mutex mutex;
-thread_local std::unordered_map<int, Handle> handles;
+std::unordered_map<int, Handle> handles;
 
 } // namespace