Fix colors in the keyguard preview

Colors were inconsistent between the keyguard preview and the actual
wallpaper colors set, because the style was not accounted for. Adjust to
account for style when rendering keyguard preview.

Flag: NONE
Bug: 308947090
Test: manually verified with different wallpapers
Change-Id: Ifc362d1f878a2e7692c275295821b305fa3eb8fe