[msan] Extend VAArgTLSOverwrite test.

This test now covers LLVM r189104.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@189105 91177308-0d34-0410-b5e6-96231b3b80d8
[dfsan] Integration test for the equal-labels case

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@189134 91177308-0d34-0410-b5e6-96231b3b80d8