Fix configtest when vcl_dir is specified
Fix configtest when vcl_dir is specified

Reported and diff submitted by Gauthier Delacroix on varnish-dev.

ajasty-cavium/Varnish-Cache,ajasty-cavium/Varnish-Cache,zhoualbeart/Varnish-Cache,chrismoulton/Varnish-Cache,feld/Varnish-Cache,varnish/Varnish-Cache,gquintard/Varnish-Cache,varnish/Varnish-Cache,feld/Varnish-Cache,ajasty-cavium/Varnish-Cache,chrismoulton/Varnish-Cache,gquintard/Varnish-Cache,zhoualbeart/Varnish-Cache,zhoualbeart/Varnish-Cache,franciscovg/Varnish-Cache,gquintard/Varnish-Cache,zhoualbeart/Varnish-Cache,franciscovg/Varnish-Cache,feld/Varnish-Cache,zhoualbeart/Varnish-Cache,varnish/Varnish-Cache,ajasty-cavium/Varnish-Cache,chrismoulton/Varnish-Cache,franciscovg/Varnish-Cache,franciscovg/Varnish-Cache,feld/Varnish-Cache,chrismoulton/Varnish-Cache,chrismoulton/Varnish-Cache,franciscovg/Varnish-Cache,varnish/Varnish-Cache,gquintard/Varnish-Cache,feld/Varnish-Cache,ajasty-cavium/Varnish-Cache,varnish/Varnish-Cache