python3: Add missing get_running_config_item binding

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
lxc-ls: Add a few new columns

This adds support for:
 - memory (total memory)
 - ram
 - swap
 - apparmor (running aa_profile)
 - selinux (running se_context)

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