Simplify the attributes '<' comparison function.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175235 91177308-0d34-0410-b5e6-96231b3b80d8
Fix testcase for attribute ordering.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175236 91177308-0d34-0410-b5e6-96231b3b80d8