Update unpaused udfps alpha when showing udfps bouncer

This will make sure the alpha is updated correctly before
showing the udfps affordance.

This CL also updates the dumpsys to be more accurate of the
actual alpha value being used.

Test: manual, atest UdfpsKeyguardViewControllerTest
Fixes: 197160246
Merged-In: I86a73dacfd2fc4f5b910e1e1e4f6535e91d00da3
Change-Id: I86a73dacfd2fc4f5b910e1e1e4f6535e91d00da3
(cherry picked from commit a73d30e2)