Revert "[LTO] Enable module summary emission by default for regular LTO"

This is breaking a couple of buildbots. We need to run the
NameAnonGlobal pass for regular LTO now as well (since we're producing a
summary). I'll post a separate patch for review to make this happen and
then re-commit.

This reverts commit c0759b7b1f4a81ff9021b952aa38a222d5fa4dfd.

llvm-svn: 335291