Always show backup settings (even if backup is deactivated).

Previously,
1) we showed backup settings for main users (including secondary non-profile users) only
when backup was activated
2) for profile users, we always showed backup settings.

However, this results in a nullpointer when opening Settings when backup is deactivated
for both main and profile user.
This CL fixes that nullpointer(and also changes existing functionality since keeping
existing functionality and fixing the nullpointer would be too large a code change)

For more details, see https://b.corp.google.com/issues/129843872#comment9 and
https://b.corp.google.com/issues/129843872#comment12


Bug: 129843872

Test: 1. atest -v UserBackupSettingsActivityTest
2. atest -v BackupInactivePreferenceControllerTest
3a) backup not active for main and profile user. shows "isn't active" for both
3b) backup active for main only. shows backup settings for main user and "isn't active" for profile.
3c) backup active for both. shows backup settings for both.
3d) backup active for profile only is not possible (as profile backup is only active when main
user backup is active). if we try to force set it, we get "isn't active" for both
3e) backup not active for secondary user. shows "isn't active"
3f) backup active for secondary user. shows backup settings.


Change-Id: Icb87a047068d29eda560c45dfa4ae02bc991b1af