Unlocking children profile must pass on existing challenge

The challenge must be passed on, otherwise LSS will generate, invalidate,
and revoke the challenge that's passed from places like FaceSettings.

Bug: 134834442

Test: duplicate generate/revoke challenge not seen anymore
Test: with work profile enrolled and owner profile non-enrolled,
      trying to enroll for owner profile works now

Change-Id: I0d38390bd5e0ee38a615d17f44d18ffa410904aa