Fixing more -Wcast-qual warnings; NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221782 91177308-0d34-0410-b5e6-96231b3b80d8
Fix the test.

It was broken since r221708.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221783 91177308-0d34-0410-b5e6-96231b3b80d8
Reduce code duplication a bit. NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221785 91177308-0d34-0410-b5e6-96231b3b80d8