Only clipping heads up that are not the first ones

Previously we would clip even the first heads up
notification which would lead to the notification being
clipped. This would happen if a notification would be
before the first heads up which could happen temporarily.

Fixes: 	138467810
Test: Add 2 heads up notifications that are not dismissable, swipe away the first, observe no clipping
Change-Id: I13f681a0a09a9de8e948fb666ee99718df3bae02