Fixing a flake when workspace loading never finishes.

The flake was caused by the fact that addOnDrawListener(), the redraw is not guaranteed. This ultimately results to the workspace loading never finishing.
Forcing the redraw.

Bug: 267200150
Test: atest Launcher3Tests:com.android.launcher3.celllayout.ReorderWidgets#simpleReorder --rerun-until-failure
Flag: N/A
Change-Id: I47683425150a07ab2632e2bebdeca4d304e30d1b