Fix biometric content overlap with top/bottom bars

Sets a solid background for the status and footer bar shown on each of
the biometric enroll introduction screens, to prevent the content from
showing through.

Test: Manually tested face and fingerprint enrollment

Fixes: 189075189
Change-Id: I1a41dc911c5ac7ded94e33b25a9c0e990e93ba3f
1 file changed