godoc: don't print spurious suggestion when running "go doc foo"
godoc: don't print spurious suggestion when running "go doc foo"

Fixes issue 3041.

R=rsc
CC=golang-dev
http://codereview.appspot.com/5671087
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go