Move the override handling to the top.
Move the override handling to the top.

In cases where the override function is used for actual users, not just
testing/overriding, it makes sense to not run the regular expressions.

Reported by: Sergey Syrota

varnish/varnish-devicedetect,wikp/varnish-devicedetect,kevinquinnyo/varnish-devicedetect,wikp/varnish-devicedetect,varnish/varnish-devicedetect,kevinquinnyo/varnish-devicedetect