Fix LocationForWorkPreferenceControllerTest

* If the location is disabled by admin, then the
  preference is disabled and the toggle is no
  longer shown. This means that setChecked is no
  longer called and the verify statement can be removed.
* If the location is off, the summary should be
  'Location is off' rather than 'off'. The verify
  statement is now updated with the correct summary.

Bug: 148755845
Test: atest com.android.settings.location.LocationForWorkPreferenceControllerTest
Change-Id: I089be0c4f8e8ec8c10160771055730289d72c8ed