[acc_tracer] Do not rewrite the leaf modules (#71790)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/71790
If a leaf module is specified, it means we should treat it as a blackbox and we should just avoid rewriting it too.
Test Plan:
```
buck test caffe2/test:test_fx_acc_tracer
```
with a new unit test.
Reviewed By: jfix71, houseroad, wushirong
Differential Revision: D33731903
fbshipit-source-id: 0560d9e8435b40f30d9b99dc3b2f47d1a04eb38b
(cherry picked from commit 747e9e44ee1792bd6ac5089ced4ffe5f43b09316)
