If firewalld is not installed (or I suppose not running), firewalld was
producing an error in the daemon init logs, even though firewalld is not
required for iptables stuff to function.
The firewalld library code was also logging directly to logrus instead
of returning errors.
Moved logging code higher up in the stack and changed firewalld code to
return errors where appropriate.
Signed-off-by: Brian Goff <cpuguy83@gmail.com>
The `--userland-proxy` daemon flag makes it possible to rely on hairpin
NAT and additional iptables routes instead of userland proxy for port
publishing and inter-container communication.
Usage of the userland proxy remains the default as hairpin NAT is
unsupported by older kernels.
Signed-off-by: Arnaud Porterie <arnaud.porterie@docker.com>
