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
Sync with Oslo-Incubator

oslo-incubator HEAD was 2eab986ef3c43f8d1e25065e3cbc1307860c25c7

This change brings in a few minor updates to python3 and a bug fix
for deep copy failure in gettextutils.

Change-Id: Id360f3b43d1ad2f67b328206990dd6bdb53c1cd7
Merge "Support IPv6 when booting instances"
Merge "Sync with Oslo-Incubator"