confine.lib: do not configue lxc isolated interfaces if parent interface does not exist, let confine_sliver_remove also remove unfinished lxc state
confine/*.lua: let sliver.set_state only override slice.set_state if less advanced
confine.lib: enable MASQUERADING on local network for private-interface sliver IPs
confine: lxc/scripts/openwrt-confine.sh enable openwrt-based slivers private interface default route and dns