Fix FaceSettings UI problem

Update the visibility of button in onStart to avoid missing check
state if Fragment & Activity were restarted

Bug: 269553342
Test: 1. enroll face
      2. go to settings > Security  privacy > device lock > face & fingerprint unlock
      3. Eenter screen lock
      4. Click face unlock > delete face model
      5.re-enroll face
      6.check the UI of face unlock detailed page
Change-Id: I152467afe2cc90932a53fe73b541e97b5b742831