[2.20-Build 64] DHCP Option 3 is not working

[Daisuke Nakajima]

vRouter does set DHCP option 3 at dhcp ACK packet when "default_gateway": set as "0.0.0.0".
If "default_gateway": has any IP address, vrouter sets "default_gateway" IP address as DHCP option 3.

### Related case "https://bugs.launchpad.net/juniperopenstack/+bug/1483105"

{
    "virtual-network": {
        "display_name": "dhcp1",
        "flood_unknown_unicast": false,
        "fq_name": [
            "default-domain",
            "common_max",
            "dhcp1"
        ],
        "href": "http://172.27.113.209:8082/virtual-network/1ced9853-9cb9-4a9e-802c-8d93a27b0ffc",
        "id_perms": {
            "created": "2015-08-11T11:01:47.452651",
            "creator": null,
            "description": null,
            "enable": true,
            "last_modified": "2015-08-11T11:01:47.576214",
            "permissions": {
                "group": "admin",
                "group_access": 7,
                "other_access": 7,
                "owner": "admin",
                "owner_access": 7
            },
            "user_visible": true,
            "uuid": {
                "uuid_lslong": 9235912601055727612,
                "uuid_mslong": 2084489687421504158
            }
        },
        "is_shared": false,
        "name": "dhcp1",
        "network_ipam_refs": [
            {
                "attr": {
                    "ipam_subnets": [
                        {
                            "addr_from_start": true,
                            "allocation_pools": [],
                            "default_gateway": "0.0.0.0",
                            "dhcp_option_list": {
                                "dhcp_option": [
                                    {
                                        "dhcp_option_name": "3",
                                        "dhcp_option_value": "50.0.0.100"
                                    }
                                ]
                            },
                            "dns_server_address": "50.0.0.2",
                            "enable_dhcp": true,
                            "host_routes": {
                                "route": []
                            },
                            "subnet": {
                                "ip_prefix": "50.0.0.0",
                                "ip_prefix_len": 24
                            },
                            "subnet_uuid": "e2122006-0986-4510-ac03-954cae52b21b"
                        }
                    ]
                },
                "href": "http://172.27.113.209:8082/network-ipam/644962c8-b54f-497b-b3b1-7cb901fe59b6",
                "to": [
                    "default-domain",
                    "default-project",
                    "default-network-ipam"
                ],
                "uuid": "644962c8-b54f-497b-b3b1-7cb901fe59b6"
            }
        ],
        "parent_href": "http://172.27.113.209:8082/project/274437e7-73b2-4de5-9130-f40bf35cdc66",
        "parent_type": "project",
        "parent_uuid": "274437e7-73b2-4de5-9130-f40bf35cdc66",
        "route_target_list": {},
        "router_external": false,
        "routing_instances": [
            {
                "href": "http://172.27.113.209:8082/routing-instance/c8d34e96-53fa-45b9-afaf-2e841e657cb4",
                "to": [
                    "default-domain",
                    "common_max",
                    "dhcp1",
                    "dhcp1"
                ],
                "uuid": "c8d34e96-53fa-45b9-afaf-2e841e657cb4"
            }
        ],
        "uuid": "1ced9853-9cb9-4a9e-802c-8d93a27b0ffc",
        "virtual_network_network_id": 5,
        "virtual_network_properties": {
            "allow_transit": false,
            "forwarding_mode": "l2_l3"
        }
    }
}

[Hari Prasad Killi (haripk)]

This is handled as part of https://bugs.launchpad.net/juniperopenstack/+bug/1483105.