Simplify do-fetch, and remove now unused code.

Turns out that the DEFAULT, and other groups sites were handled in
a different way, ending up having the same code twice, but in
slightly different places.

PR: 210198
Submitted by: mat
Exp-run by: antoine
Sponsored by: The FreeBSD Foundation, Absolight
Differential Revision: https://reviews.freebsd.org/D6779