zebra: json support for show ip nht

zebra: json support for show ip nht

show ip/ipv6 nht vrf <all | name> json support added.

Commands enhanced with JSON:
----------------------------
show ip nht json
show ip nht <addr> json
show ipv6 nht json
show ipv6 nht <addr> json
show ip nht vrf <name> json
show ip nht vrf all json
show ipv6 nht vrf <name> json
show ipv6 nht vrf all json
show ip nht vrf default <addr> json
show ipv6 nht vrf default <addr> json

Sample JSON output:
-------------------

tor-1# show ip nht vrf default json
{
  "default":{
    "nexthops":{
      "27.0.0.5":{
        "nhtConnected":false,
        "clientList":[
          {
            "protocol":"bgp",
            "socket":70,
            "protocolFiltered":"none"
          }
        ],
        "gates":[
          {
            "ip":"fe80::202:ff:fe00:2b",
            "interface":"uplink_1"
          },
          {
            "ip":"fe80::202:ff:fe00:35",
            "interface":"uplink_2"
          }
        ],
        "resolvedProtocol":"bgp"
      },
      "27.0.0.6":{
        "nhtConnected":false,
        "clientList":[
          {
            "protocol":"bgp",
            "socket":70,
            "protocolFiltered":"none"
          }
        ],
        "gates":[
          {
            "ip":"fe80::202:ff:fe00:2b",
            "interface":"uplink_1"
          },
          {
            "ip":"fe80::202:ff:fe00:35",
            "interface":"uplink_2"
          }
        ],
        "resolvedProtocol":"bgp"
      }
    }
  }
}

tor-1# show ipv6 nht vrf default json
{
  "default": {
    "nexthops": {
      "fe80::202:ff:fe00:25": {
        "nhtConnected": true,
        "clientList": [
          {
            "protocol": "bgp",
            "socket": 45,
            "protocolFiltered": "none"
          }
        ],
        "gates": [
          {
            "interface": "swp1",
            "directlyConnected": true
          }
        ],
        "resolvedProtocol": "connected"
      },
      "fe80::202:ff:fe00:2b": {
        "nhtConnected": true,
        "clientList": [
          {
            "protocol": "bgp",
            "socket": 45,
            "protocolFiltered": "none"
          }
        ],
        "gates": [
          {
            "interface": "swp1",
            "directlyConnected": true
          }
        ],
        "resolvedProtocol": "connected"
      }
    }
  }
}

tor-1# show ipv6 nht vrf all json
{
  "default": {
    "nexthops": {
      "fe80::202:ff:fe00:25": {
        "nhtConnected": true,
        "clientList": [
          {
            "protocol": "bgp",
            "socket": 45,
            "protocolFiltered": "none"
          }
        ],
        "gates": [
          {
            "interface": "swp1",
            "directlyConnected": true
          }
        ],
        "resolvedProtocol": "connected"
      },
      "fe80::202:ff:fe00:2b": {
        "nhtConnected": true,
        "clientList": [
          {
            "protocol": "bgp",
            "socket": 45,
            "protocolFiltered": "none"
          }
        ],
        "gates": [
          {
            "interface": "swp1",
            "directlyConnected": true
          }
        ],
        "resolvedProtocol": "connected"
      }
    }
  },
  "mgmt": {
    "nexthops": {}
  },
  "sym_1": {
    "nexthops": {}
  }
}

Ticket:#3229013
Issue:3229013

Testing Done: Unit test completed.

Signed-off-by: Chirag Shah <chirag@nvidia.com>
Signed-off-by: Sindhu Parvathi Gopinathan <sgopinathan@nvidia.com>