SystemUI: Fix auth scrim turning black in white theme

before:
https://i.imgur.com/cA6rlEm.png
https://i.imgur.com/UR8h7l1.png

after:
https://i.imgur.com/2fSfU2W.png
https://i.imgur.com/k1SBPdX.png



Change-Id: I6829f8179b1e28e58ec36c9225fb6a63b64c8c16
Signed-off-by: Jyotiraditya Panda <jyotiraditya@aospa.co>

Fix AUTH_SCRIMMED state too.

Change-Id: I3262b5bac4ce3202704003eaffdfde13f860265e