This test is currently too flakey on openbsd/arm - ignore failures for the time
being.

Change-Id: Ia334d188f505167e691177ebe2c7a2df54bf556a
Reviewed-on: https://go-review.googlesource.com/c/153579Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>