Automatic merge from submit-queue

util/iptables: grab iptables locks if iptables-restore doesn't support --wait

When iptables-restore doesn't support --wait (which < 1.6.2 don't), it may
conflict with other iptables users on the system, like docker, because it
doesn't acquire the iptables lock before changing iptables rules. This causes
sporadic docker failures when starting containers.

To ensure those don't happen, essentially duplicate the iptables locking
logic inside util/iptables when we know iptables-restore doesn't support
the --wait option.

Unfortunately iptables uses two different locking mechanisms, one until
1.4.x (abstract socket based) and another from 1.6.x (/run/xtables.lock
flock() based).  We have to grab both locks, because we don't know what
version of iptables-restore exists since iptables-restore doesn't have
a --version option before 1.6.2.  Plus, distros (like RHEL) backport the
/run/xtables.lock patch to 1.4.x versions.

Related: https://github.com/kubernetes/kubernetes/pull/43575
See also: https://github.com/openshift/origin/pull/13845
Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1417234

@kubernetes/rh-networking @kubernetes/sig-network-misc @eparis @knobunc @danwinship @thockin @freehan