Description of problem: There should be support for ovn-nbctl to add static ARP entries into a logical router. Today the only way to do this is to use ovn-sbctl aand create an entry in the mac binding table like: https://github.com/ovn-org/ovn-kubernetes/pull/1363/files#diff-04a3ee61bce76dbc7d0f583289d5f608R353
upstream patch: http://patchwork.ozlabs.org/project/ovn/patch/257bf842bac8d1e3eb2ec40ac11cd31a98c556e1.1632853104.git.lorenzo.bianconi@redhat.com/
upstream commit: https://github.com/ovn-org/ovn/commit/b22684d4e37c3dd205a959925b6e3f1827bbe045