AOD: Keep doze brightness when unlocking with fingerprint

Updates the logic that was already in place to prevent lighting up
the display before the unlock transition starts:
- treat AOD as pulsing in FingerprintUnlockController
- now that doze can use more than one brightness level, use the current

Bug: 62885451
Test: Unlock with fingerprint from AOD. Observe that the unlock transition does not prematurely change the brightness level
Change-Id: I266bd5e4c0a1d5b4c347a65c0e7936247e333cfc