OnScrollListener fix in AbsListView

Starting from a list at position 0 (first element displayed
at the top), touch and scroll down. The list cannot go further
down and the glow is displayed.

A connecter scrollListener will receive a FLING but will not
receive the IDLE after.

The reason is that the springback motion that should be started
at that point is not started because the overscroll distance is set to 0.

The fix is to report an IDLE state in that case.

Change-Id: I383babaf8412ee74d598efcf61e91cff44068c79