lxc-ls: Detect missing setns support

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
python3: unpriv containers

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
debug

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>