make nerdctl network inspect compatible with Docker

[AkihiroSuda]

Now nerdctl network inspect uses --mode=dockercompat by default.

$ nerdctl network inspect compose-wordpress_default
[
    {
        "Name": "compose-wordpress_default",
        "Id": "19",
        "IPAM": {
            "Config": [
                {
                    "Subnet": "10.4.19.0/24",
                    "Gateway": "10.4.19.1"
                }
            ]
        },
        "Labels": {
            "com.docker.compose.network": "default",
            "com.docker.compose.project": "compose-wordpress"
        }
    }
]

Can be rolled back to the old behavior by specifying --mode=native.

$ nerdctl network inspect --mode=native compose-wordpress_default
[
    {
        "CNI": {
            "cniVersion": "0.4.0",
            "name": "compose-wordpress_default",
            "nerdctlID": 19,
            "nerdctlLabels": {
                "com.docker.compose.network": "default",
                "com.docker.compose.project": "compose-wordpress"
            },
            "plugins": [
                {
                    "type": "bridge",
                    "bridge": "nerdctl19",
                    "isGateway": true,
                    "ipMasq": true,
                    "hairpinMode": true,
                    "ipam": {
                        "type": "host-local",
                        "routes": [
                            {
                                "dst": "0.0.0.0/0"
                            }
                        ],
                        "ranges": [
                            [
                                {
                                    "subnet": "10.4.19.0/24",
                                    "gateway": "10.4.19.1"
                                }
                            ]
                        ]
                    }
                },
                {
                    "type": "portmap",
                    "capabilities": {
                        "portMappings": true
                    }
                },
                {
                    "type": "firewall"
                },
                {
                    "type": "tuning"
                },
                {
                    "type": "isolation"
                }
            ]
        },
        "NerdctlID": 19,
        "NerdctlLabels": {
            "com.docker.compose.network": "default",
            "com.docker.compose.project": "compose-wordpress"
        },
        "File": "/home/suda/.config/cni/net.d/nerdctl-compose-wordpress_default.conflist"
    }
]

[AkihiroSuda]

@fahedouch @ktock PTAL

[ktock]

error doesn't seems to used here?

[AkihiroSuda]

True, but not new in this file. And a future version of this function may return an error.

[ktock]

LGTM

[fahedouch]

LGTM