www/varnish4 www/varnish5: Change default hash algorithm

The default hash algorithm as of Varnish 2.1 is "critbit". The FreeBSD
varnish ports/packages have run the varnish daemon with the "classic"
algorithm due to an oversight. This update corrects the default to
adhere to the recommendation of upstream.

Submitted by: Mark Staudinger <mark staudinger AT nyi net>