Code cleanup around exception handling and stack walking.

- Remove unused code setting the method and dex pc below an upcall.
- Clear cur_oat_quick_method_header when stack walking to be consistent
  in having a runtime method and a null oat method header.

Test: test.py
Change-Id: I87672d193eb2e62add3ae7b8a42f2202e8eb927c
3 files changed