Test is not run in short mode, except on builders.

Change-Id: I4456830770188951e05ac13669e834a25bf569ae
Reviewed-on: https://go-review.googlesource.com/55973
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Joe Tsai <joetsai@google.com>
Reviewed-by: Joe Tsai <joetsai@google.com>
Reviewed-by: Marvin Stenger <marvin.stenger94@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>