Some functions in log/syslog depend on syslogd running. Instead of
treating errors caused by the daemon not running as test failures,
ignore them and skip the test.

Fixes the longtest builder.

Change-Id: I628fe4aab5f1a505edfc0748861bb976ed5917ea
Reviewed-on: https://go-review.googlesource.com/113838
Run-TryBot: Alberto Donizetti <alb.donizetti@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>