net: Don't allow net_add for netns-less containers

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
ct: Assign root pid before starting net

Network config may need to know one to assign net device.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
libnetlink: Basic libnetlink engine

Taken from LXC, CRIU and iproute2

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
net: Implement assigning host nic to ct call

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
test: Add test for hostnic networking

Add a dummy device and check it's there.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>