[msan] Clean stack and TLS shadow on thread exit.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@197156 91177308-0d34-0410-b5e6-96231b3b80d8
[msan] Add a check for recursive __msan_init.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@197218 91177308-0d34-0410-b5e6-96231b3b80d8