cmd/fix: revert IPv6 scoped address zone support of IPNet

R=golang-dev, bradfitz
CC=golang-dev
https://codereview.appspot.com/7554051
net: make use of reflect.DeepEqual in IP manipulation tests

Also applies camel style to test case holders.

R=golang-dev, r
CC=golang-dev
https://codereview.appspot.com/7884043