Fix clang tests to be compliant with LLVM IR aliases

Comdat IR references were mistakenly printed for aliases when they
passed through the IR/AsmWriter code.

This makes clang's tests not check for the existance of these wrongly
printed comdat references.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@212733 91177308-0d34-0410-b5e6-96231b3b80d8