ua: Listen to the right dbus name to show the magnifier option.  This
reveals a fairly broken zoom options menu that we've never seen before.
many of the options are broken (Which I think is because our magnifier
code from cinnamon is a few versions older than the control center code
(which is 3.6 or 3.8).

We should temporarily trim out the broken bits, then for 2.4 bring
the cinnamon magnifier up to date a bit and restore them.