Ignore whitelisted files when they are within a symlinked directory
Fixes: https://gitlab.com/gitlab-org/gitlab-ce/issues/20476
Keeping the realpath check allows us to ignore symlinks that point to the cacert, if the user ran c_rehash themselves int he certs directory, the non realpath version works if the whitelisted file itself is a symlink, or rather, is within a symlinked directory.