A manager for the ebtables utility. An ebtables manager
is needed for an additional patch, which will close an
ARP cache poisoning loophole.

While there are similarities between iptables-manager and
ebtables-manager, these have not been factored out, since
the iptables-manager code is sensitive and it's not
desirable to modify it at this time.

The implementation of the ebtables manager comes in large
part from an abandoned patch provided by Édouard Thuleau, which
he presented for review here:

        https://review.openstack.org/#/c/70067/

Credit for the workin of the ebtables manager should go to
Édouard, I merely ported it to today's code.

Related-bug: 1274034
Co-authored-by: Thuleau Édouard <edouard.thuleau@cloudwatt.com>
Merge branch 'jb_icehouse_arp_patch' of github.com:CiscoSystems/neutron into jb_icehouse_arp_patch

Conflicts:
	neutron/agent/linux/ebtables_manager.py