seccomp not applying?

gistfile1.txt

Given this profile:
```
cat b.json
{
    "defaultAction": "SCMP_ACT_ALLOW",
    "architectures": [
        "SCMP_ARCH_X86_64",
        "SCMP_ARCH_X86",
        "SCMP_ARCH_X32"
    ],
    "syscalls": [
        {
            "name": "chmod",
            "action": "SCMP_ACT_ERRNO",
            "args": []
        },
        {
            "name": "chown",
            "action": "SCMP_ACT_ERRNO",
            "args": []
        },
        {
            "name": "chown32",
            "action": "SCMP_ACT_ERRNO",
            "args": []
        }
    ]
}
```

I would have expected the following container to fail as seccomp has blocked seccomp.
```
> docker run --rm -it --security-opt seccomp:b.json ubuntu chmod 400 /etc/hostname
> echo $?
0
```

Behaviour on a different machine. Seccomp is only being applied if I set a user too.

> sudo docker run --rm -it -u 1000 --security-opt seccomp:b.json ubuntu chmod 400 /etc/hostname
chmod: changing permissions of '/etc/hostname': Operation not permitted

> sudo docker run --rm -it  --security-opt seccomp:b.json ubuntu chmod 400 /etc/hostname
> echo $?
0