auto-update: no test pins old-key rename before admin-policy defaults #44

Minor from the data-integrity DI-2 r4 lens on #5: #5 (comment)

The settings load renames the old auto-update keys before it fills in admin-policy defaults. That order is correct,
but no test pins it. If the two steps were swapped and an admin policy set the default to on, an old settings file
that said off would load as on (updates turning on without the user choosing it).

Fix: one test that loads an old-name file with the value off under an admin policy default of on, and expects off.