cfdisk fails to zap mac partition table

When a disk has a mac partition table and you run cfdisk on it, it creates a new msdos partition table, but preserves the mac partition table's signature, probably because it is in the area where the mbr boot code is. When initializing a new MBR, cfdisk should not preserve any existing data. fdisk does not exhibit this behavior.

To reproduce with a clean loop device:

parted /dev/loop0 mklabel mac
cfdisk /dev/loop0
parted /dev/loop0 print

Parted still recognizes the mac partition table.

The original bug report can be seen here: https://bugs.launchpad.net/bugs/909424