Do not show soft keyboard when locked out

- Remove stateVisible for ConfirmLockPassword activity so that
  soft keyboard does not auto show up when the activity starts;
- Programatically show/hide soft keyboard when ConfirmLockPassword
  activity window gains focus;

Bug:20542149
Change-Id: I3faa20312d2d25752bd35b70dc8ed785e7687f0a