Reset SSA animationProperties on each animation pass

SSA was leaking custom interpolators set from previous passes on
starting animation events, which led to weird animations. This CL
resets custom interpolators on each pass.

Fixes: 334096683
Flag: com.android.systemui.notifications_improved_hun_animation
Test: post some HUNs, wait until they stop HUNning, open the shade,
check their expand/collapse and dismiss animations

Change-Id: I6cc087a26b3903cde866b6fc7db754fcaf18d048