Some rewrites to simplify logical operations.

Fixes #14363

Change-Id: I45a1e8f227267cbcca0778101125f7bab776a5dd
Reviewed-on: https://go-review.googlesource.com/22188Reviewed-by: Alexandru Moșoi <alexandru@mosoi.ro>
Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro>
TryBot-Result: Gobot Gobot <gobot@golang.org>