You cannot do that with pure CSS, but it's easy to achieve with jQuery.
So when you hover over a child, you do not want to amend the parent.
https://jsfiddle.net/8nqfLgsk/2/
$(".list-categories li a").hover( function(){
$(this).toggleClass("active-btn");
});
Basically with this, you're only adding a class to the element which you're hovering over, without amending parent.