Fixed a regression where custom notification where unreadable

Because custom notifications don't have their background
Color reapplied, we need to ensure that the color is saved.

Test: runtest -x packages/SystemUI/tests/src/com/android/systemui/statusbar/NotificationCustomViewWrapperTest.java
Change-Id: I309097ef8abe18706479d64c6048521f941a26f5
Fixes: 34861088