Trebuchet: Revert animation end

Since moveToDefaultScreen is protected by mIsSwitchingState, no animation is triggered when
the home screen is double tapped. Now, cancel the animation is causing icons to disappear.

Change-Id: I12fd3a8b0b71139b5744e462e97774d4c13e6466
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>