[MSan] Disable sanitization for __sanitizer_dtor_callback.

Summary:
Eliminate unnecessary instrumentation at __sanitizer_dtor_callback
call sites.  Fixes https://github.com/google/sanitizers/issues/861.

Reviewers: eugenis, kcc

Reviewed By: eugenis

Subscribers: vitalybuka, llvm-commits, cfe-commits, hiraditya

Differential Revision: https://reviews.llvm.org/D38063

llvm-svn: 313831