Fixes (skips) the test on Android, where stdout/stderr are not
terminals.

Updates #18153

Change-Id: Ieca65150362a5c423747ad751e00f76f0b890746
Reviewed-on: https://go-review.googlesource.com/35957
Run-TryBot: Elias Naur <elias.naur@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>