The android builders are failing on the AF_UNIX part of the new splice
test from CL 113997. Skip them.

Change-Id: Ia0519aae922acb11d2845aa687633935bcd4b1b0
Reviewed-on: https://go-review.googlesource.com/133515
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>