Not 100% sure why it was flickering, but I do know that the
flicker started happening after putting this into a separate
thread, and that with that change it doesn't flicker anymore,
ever.
Adds 0.5ms while unlocking but at this point this is a good trade-
off to make.
Test: Unlock device with FP
Change-Id: I736a3c64d9b63df9d6cdcb7855bde13a19560a83
Fixes: 62380221
e3e0b06a12