NotificationPanelView observe weird gradient in Landscape mode

QSContainerImpl did not gone backgroundGradient in Landscape after
enable again.
This gradient showing improperly make the Visual bad.
We add pocliy in disable() to make sure bkgGradient visibility sync the
state of orientation change.

Test: atest SystemUITests
      Manual test, send notify in landscape reply->back->looks good
Bug: b/109852519
Change-Id: Ia368787d277d44062b6c95aed46848ac51509b5e