Show QS footer background when QS starts to show.

Fading in the QS footer starts at the end of QS expansion animation.
This makes the UMO flick. Adjusting the delay of showing the QS footer
background to start after the QS starts to show fixes the issue and
avoids the occurance of b/240563302.

Flag: NONE
Bug: 300369748
Test: atest FooterActionsViewModelTest.
Test: Checked UI, make sure the flicks effects doesn't show and we avoid b/240563302 as well.
Change-Id: I4abe6517f4ed52f0e85d0d03b532920482cd1b5c