[PATCH] [sanitizer] Fix log_path behavior with StopTheWorld.

[Sergey Matveev]

  Alternatively, we could reuse the parent's file descriptor. Both approaches are equally ugly IMO.

  Incidentally, this code appears to be funamentally racy (even before my patch) because MaybeOpenReportFile can be called from multiple threads at once.

http://llvm-reviews.chandlerc.com/D2306