nplan-configured LXD container appears to behave as expected: on a setup with IPv6 enabled, I get an IPv6 address on the container without a startup delay. In a host with IPv6 disabled on the lxd bridge, the container also starts up appropriately, with no IPv6 address, as expected.
Verification-done on xenial: nplan 0.32~16.04.5
nplan-configured LXD container appears to behave as expected: on a setup with IPv6 enabled, I get an IPv6 address on the container without a startup delay. In a host with IPv6 disabled on the lxd bridge, the container also starts up appropriately, with no IPv6 address, as expected.