Ensure /etc/sudoers sed replacement works for Debian 7.x.

Debian 7's `/etc/sudoers` file format has changed, requiring an update to the sed regex in the `sudoers.sh` script.

As this is only specific to this definition, I've removed the symlink to the common `debian/sudoers.sh` and created a new `sudoers.sh` file with the required updates.