SetupWizard: Disable mobile data at least once

* Right now, the user has to set the toggle on and off to actually get
  the setting set to "off", since the underlying default value is "on"
* Make sure to send an "off" initially right at the beginning of SuW

Change-Id: Iec2fd05ea341351f3e6d4b195a1a385f9d88d4f7
(cherry picked from commit 29e77749)