Disabled by https://golang.org/cl/53020044 due to false positives.
Reenable and model properly.

Fixes #17306.

Change-Id: I28405ddfcd17f58cf1427c300273212729154359
Reviewed-on: https://go-review.googlesource.com/31589
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>