Update config to support LXC (Linux Containers)

These configurations enable usage of `lxc` and `docker` in the raspberrypi. The flags were chosen by running `lxc-checkconfig` and activating the missing features. This is the result of `lxc-checkconfig` before these changes:

```
--- Namespaces ---
Namespaces: enabled
Utsname namespace: enabled
Ipc namespace: enabled
Pid namespace: enabled
User namespace: missing
Network namespace: enabled
Multiple /dev/pts instances: missing

--- Control groups ---
Cgroup: enabled
Cgroup clone_children flag: enabled
Cgroup device: enabled
Cgroup sched: enabled
Cgroup cpu account: enabled
Cgroup memory controller: enabled

--- Misc ---
Veth pair device: missing
Macvlan: enabled
Vlan: enabled
File capabilities: enabled
```