Resetting notification roundness when the snapback animation overshoots.

This occurs in the update listener of the SwipeHelper, when the value
changes its direction of change. The NSSL controller reacts to the event
by resetting the roundness.

Test: manual. Verified UI change when notifications snap back.
Flag: com.android.systemui.magnetic_notification_swipes
Bug: 390179908
Change-Id: I8e39ecd54e4e40ae1e5d5120261463f2e4dfefde