[asan] Improve thread lifetime tracking on POSIX systems.

Call AsanThread::Destroy() from a late-running TSD destructor.
Previously we called it before any user-registered TSD destructors, which caused
false positives in LeakSanitizer.

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@192585 91177308-0d34-0410-b5e6-96231b3b80d8