The leading underscores aren't necessary.

Change-Id: I1d4c4b681e2a29ef40a0a6cf705c3b17a49c9f65
Reviewed-on: https://go-review.googlesource.com/40873
Run-TryBot: Michael Munday <munday@ca.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>