{{commit e050e63c6c846afe1a8f54a214702ce74f538951

ovn-northd: Add CoPP policies for flows that punt packets to ovn-controller.

Change the ovn-northd implementation to set the new 'controller_meter'
field for flows that need to punt packets to ovn-controller.

Protocol packets for which CoPP is enforced when sending packets to
ovn-controller (if configured):

• ARP
• ND_NS
• ND_NA
• ND_RA
• DNS
• IGMP
• packets that require ARP resolution before forwarding
• packets that require ND_NS before forwarding
• packets that need to be replied to with ICMP Errors
• packets that need to be replied to with TCP RST
• packets that need to be replied to with DHCP_OPTS
• packets that trigger a SCTP abort action
• contoller_events
• BFD}}

ovn-kubernetes should enable CoPP to prevent DoS of ovn-controllers when responding to various incoming packets. Enabling consists of creating "meters" for packet types and then using those meters in the "copp" table in the OVN Northbound database. ovn-kube can do this once per startup in StartClusterMaster() or somewhere like that.

Need to double-check that all pkt_in operations in ovn-controller are protected by CoPP too.