Revert "[ThinLTO] Rename COMDATs for COFF when promoting/renaming COMDAT leader"

This reverts commit r352763.

Causing a couple bot failures, root cause pointed to by sanitizer bot:
http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-fast/builds/28909/steps/annotate/logs/stdio

Use after free. I understand the issue but will revert and test with fix
before recommitting.

llvm-svn: 352768