Revert "Reapply "DebugInfo: Ensure that all debug location scope chains from instructions within a function, lead to the function itself.""

This reverts commit r212776.

Nope, still seems to be failing on the sanitizer bots... but hey, not
the msan self-host anymore, it's failing in asan now. I'll start looking
there next.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212793 91177308-0d34-0410-b5e6-96231b3b80d8