Those print statements are not a good debug helpers
and only clutter the code.

Change-Id: Ifbf450a04e6fa538af68e6352c016728edb4119a
Reviewed-on: https://go-review.googlesource.com/c/go/+/160537
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>