If backup service is not available, remove Settings->Backup and Backup->"Backup is disabled by

admin" from search results.

"Backup -> Backup" still appears due to the PrivacySettingsActivity. On clicking that,
we get "Backup is disabled by admin" which is OK

Bug: 129743816

Test: 1. atest -v UserBackupSettingsActivityTest
2. atest -v BackupInactivePreferenceControllerTest
3. Create and switch to secondary user. Type "backup" in settings search. Note that only
"Backup->Backup" is shown and on clicking it, we get "Backup is disabled by admin"

Change-Id: Ic13e2d745c9511cbebe27aa4c6f5cd89b277fc37