[ThinLTO] Fix test

Fix test changes added in r335760. Even though we are invoking llvm-lto2
in single threaded mode, the order of processing the modules in the
backend is apparently not deterministic. Handle the expected debug
messages in any order. (The determinism would be good to fix, but not
related to this change.)

This also undoes the change I made in r335764 to help debug this.

llvm-svn: 335766