zebra: Show NHT resolve via default status on/off

zebra: Show NHT resolve via default status on/off

```
donatas-laptop# show ip nht
VRF default:
 Resolve via default: on
192.168.10.123
 resolved via connected
 is directly connected, wlp82s0 (vrf default)
 Client list: bgp(fd 21)
donatas-laptop# show ip nht json
{
  "default":{
    "ipv4":{
      "resolveViaDefault":true,
      "192.168.10.123":{
        "nhtConnected":false,
        "clientList":[
          {
            "protocol":"bgp",
            "socket":21,
            "protocolFiltered":"none"
          }
        ],
        "nexthops":[
          {
            "flags":3,
            "fib":true,
            "directlyConnected":true,
            "interfaceIndex":3,
            "interfaceName":"wlp82s0",
            "vrf":"default",
            "active":true
          }
        ],
        "resolvedProtocol":"connected"
      }
    }
  }
}
donatas-laptop# show ip nht vrf all

VRF default:
 Resolve via default: on
192.168.10.123
 resolved via connected
 is directly connected, wlp82s0 (vrf default)
 Client list: bgp(fd 21)
donatas-laptop# show ip nht vrf all json
{
  "default":{
    "ipv4":{
      "resolveViaDefault":true,
      "192.168.10.123":{
        "nhtConnected":false,
        "clientList":[
          {
            "protocol":"bgp",
            "socket":21,
            "protocolFiltered":"none"
          }
        ],
        "nexthops":[
          {
            "flags":3,
            "fib":true,
            "directlyConnected":true,
            "interfaceIndex":3,
            "interfaceName":"wlp82s0",
            "vrf":"default",
            "active":true
          }
        ],
        "resolvedProtocol":"connected"
      }
    }
  }
}
donatas-laptop#
```

Signed-off-by: Donatas Abraitis <donatas@opensourcerouting.org>