Defer onColorsChanged updates during widget-to-home animation

Color change updates recreate the view, which can interfere with the
widget-to-home return animation, specifically the GhostView's use of the
AppWidgetHostView's render node.

Deferring the application of color changes until the end of the
animation allows the widget to settle and remove the GhostView before a
color change might recreate the widget's view.

Bug: 190818220
Test: manual
Change-Id: I6552e583ebb0e4810077d4e70fe9ecb07fd5d01a