start: use lxc-user-nic if we are not root

start: use lxc-user-nic if we are not root

Note this results in nics named things like 'lxcuser-0p'.  We'll
likely want to pass the requested name to lxc-user-nic, but let's
do that in a separate patch.

If we're not root, we can't create new network itnerfaces to pass
into the container.  Instead wait until the container is started,
and call lxc-user-nic to create and assign the nics.

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Acked-by: Stéphane Graber <stgraber@ubuntu.com>