Merge remote-tracking branch 'remotes/otubo/tags/pull-seccomp-20180601' into staging

pull-seccomp-20180601

# gpg: Signature made Fri 01 Jun 2018 13:01:18 BST
# gpg:                using RSA key DF32E7C0F0FFF9A2
# gpg: Good signature from "Eduardo Otubo (Senior Software Engineer) <otubo@redhat.com>"
# Primary key fingerprint: D67E 1B50 9374 86B4 0723  DBAB DF32 E7C0 F0FF F9A2

* remotes/otubo/tags/pull-seccomp-20180601:
  sandbox: disable -sandbox if CONFIG_SECCOMP undefined

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>