ipv6: simplify tests and benchmarks

Change-Id: I248e5e5215960bceaba357d3d4a6e72191f955b1
Reviewed-on: https://go-review.googlesource.com/47372
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matt Layher <mdlayher@gmail.com>
2 files changed