[analyzer] Fixup for r185609: actually do suppress warnings coming out of std::list.

list is the name of a class, not a namespace. Change the test as well - the previous
version did not test properly.

Fixes radar://14317928.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@185898 91177308-0d34-0410-b5e6-96231b3b80d8