When this flag is set, then a multicast packet that would normally be
delivered to ports on multiple hypervisors is only delivered to ports
on the local hypervisor.

The primary known use case for this is when multicast packets originate
from ovn-controller. Multiple ovn-controllers will be attempting to send
out those multicast packets, and so each should only be responsible for
delivering those packets to their local ports.

Signed-off-by: Mark Michelson <mmichels@redhat.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>