Log fingerprint unlock mode

It's hard to determine why sometimes after OTA/reboot the first FP
authenticated doesn't cause bouncer to appear. Suspect calculateMode()
is returning either MODE_NONE or MODE_ONLY_WAKE but hard to verify without
log

Bug: 62444020

Test: build and look at log
Change-Id: Ie0dd9cc88bf300b06f1c85124fe98de6d3a1e6ba