Fixed not able to launch FaceSettings page when face is enrolled

Save mConfirmingPassword state

Bug: 370940762
Test: 1. Enroll face
      2. Enabled "Don't keep activity" in develop option
      3. Click "Face" item in "Device unlock" setting page
Flag: EXEMPT bug fix
Change-Id: Ie898f94f9e600b1b5c33d6923956212537173154