Description of problem:
This test is currently failing in 4.10 with the following output:

   the extra elements were
        <[]*nbdb.LogicalRouterPolicy | len:2, cap:2>: [
            {
                UUID: "c168be9b-7c43-4fcc-972c-af284cc43f2b",
                Action: "reroute",
                ExternalIDs: {"name": "egressip"},
                Match: "ip4.src == 10.128.0.15",
                Nexthop: nil,
                Nexthops: [],
                Options: nil,
                Priority: 100,
            },
            {
                UUID: "d062a239-6da0-45ed-b661-0170ca5ca0f3",
                Action: "reroute",
                ExternalIDs: {"name": "egressip"},
                Match: "ip4.src == 10.128.0.16",
                Nexthop: nil,
                Nexthops: [],
                Options: nil,
                Priority: 100,
            },
        ]

It looks like the nexthops are just being removed, rather than the entire logical route policy being deleted:

2022/06/21 15:19:33 cache: "caller"={"file":"cache.go","line":684} "level"=5 "msg"="updating row" "uuid"="ed99a05c-c2e4-4b2a-a95f-ddca4a2f6e14" "table"="Logical_Router_Policy" "old"="&{UUID:ed99a05c-c2e4-4b2a-a95f-ddca4a2f6e14 Action:reroute ExternalIDs:map[name:egressip] Match:ip4.src == 10.128.0.15 Nexthop:<nil> Nexthops:[100.64.0.2] Options:map[] Priority:100}" "new"="&{UUID:ed99a05c-c2e4-4b2a-a95f-ddca4a2f6e14 Action:reroute ExternalIDs:map[name:egressip] Match:ip4.src == 10.128.0.15 Nexthop:<nil> Nexthops:[] Options:map[] Priority:100}"

Does not happen in 4.11, so 4.10 is missing some logic to determine if we should remove nexthop or delete the entire policy.