message: Fix a memory leak in MklDnnData.
  This commit fixes leak caused by field user_memory_, which I can repro
  and verify. From reading the code, I think the same leak may happen to
  fields like reorder_memory_. Since I cannot repro or verify the later,
  I'll leave it the authors.
diff: @@ -1766,6 +1766,7 @@ class MklDnnData {
  inline void SetUsrMem(const memory::primitive_desc& pd,
  void* data_buffer = nullptr) {
  CHECK_NOTNULL(cpu_engine_);
  + if (user_memory_) delete user_memory_;
  // TODO(nhasabni): can we remove dynamic memory allocation?
  if (data_buffer) {
  user_memory_ = new memory(pd, data_buffer);
  