firewalld: Start as system service.

BUG=chromium:435400
TEST=Deploy, reboot, firewalld is running.

Change-Id: I1f10e5ccb606dd6b1f24a41e3556b8ae8002844c
Reviewed-on: https://chromium-review.googlesource.com/246272
Trybot-Ready: Jorge Lucangeli Obes <jorgelo@chromium.org>
Tested-by: Jorge Lucangeli Obes <jorgelo@chromium.org>
Reviewed-by: Zeping Qiu <zqiu@chromium.org>
Commit-Queue: Jorge Lucangeli Obes <jorgelo@chromium.org>
1 file changed