Revert "Reapply "DebugInfo: Ensure that all debug location scope chains from...

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.

llvm-svn: 212793