Fingerprint enrolling should update UI while in multi-window mode

Fixes: 67652597

Test: Try enrolling fingerprint while in multi-window mode, with and
      without focusing the FP Settings activity

Test: Enrolling doesn't occur when FP Settings activity is not shown
      (ie home button pressed)

Change-Id: Ie467da767ae36eb8d3c2b956754272749dffb43fu