nixos/test-reports: use local copy of jquery

The current way test reports get jquery,

  src="//ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"

only works when getting reports over http:// or https://, not file://.
Change it so that it works for all protocols by using a local copy of
jquery.

This fixes the issue where locally created and browsed test reports
cannot be navigated properly; clicking the '+' symbol to expand
sub-sections doesn't work.

CC: @edolstra