Support IPv6 when booting instances

When nova uses neutron, IPv6 addresses may be allocated.  This ensures
those addresses are supported.the patch to modify nova is
https://review.openstack.org/#/c/74252/

Change-Id: I2468d3bcaca9122e5d3f9c98044d57f623630dc3
Closes-bug: #1267685
Merge "Support IPv6 when booting instances"